CA2033463A1 - Polymeric thin film waveguide media - Google Patents
Polymeric thin film waveguide mediaInfo
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- CA2033463A1 CA2033463A1 CA 2033463 CA2033463A CA2033463A1 CA 2033463 A1 CA2033463 A1 CA 2033463A1 CA 2033463 CA2033463 CA 2033463 CA 2033463 A CA2033463 A CA 2033463A CA 2033463 A1 CA2033463 A1 CA 2033463A1
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- polymer
- thin film
- waveguide medium
- optical waveguide
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Abstract
ABSTRACT OF THE DISCLOSURE
This invention provides polymeric thin film optical waveguide media which exhibit nonlinear optical response, and which have utility as an optical waveguide component in all-optical and electrooptical light switch and light modulator devices.
An invention waveguide medium consists of a thin film of an amorphous organic polymer as illustrated by the following structure:
This invention provides polymeric thin film optical waveguide media which exhibit nonlinear optical response, and which have utility as an optical waveguide component in all-optical and electrooptical light switch and light modulator devices.
An invention waveguide medium consists of a thin film of an amorphous organic polymer as illustrated by the following structure:
Description
n~ss ~ 0~ Ulc J
2 ~
~~ CEL-89-167 il POLYMERIC THIN FILM WAVE~:UIDE MEDIA
CR:)SS-REFEP~ENCE TO RELATED PATENT APPLICATlO~lS
_ _ _ __ __ _ ___ __ The present patent application has ~ubject matter i related to the disclosures of copending patent application ;I S.N. 14a,262, filed January 25, 1988 patent application ¦¦ S.N. 405,503, filed September 11~ 198~ patent application ¦ S.N. ~CEL-B8-116), filed ; and patent !¦ application S.N. (CEL-88-121), filed CI:C~O~
Polymers with a comb structure of pendant side chains are a new class of organic materials which exhibit interesting optical properties.
l Comb-like liquid crystalline polymers are described in ! Eur. Polym. J., 18, 651 (1982); Advanced Polymer Science, ,¦ Liquid Crystal Polymers II~III, Springer-Verlag, New York ~ (1984), pages 215-220: and in United States Patent Numbers i 4,293,435 and 4,6 1,3~8. ~be disclosed polymeric structures have ~een developed for their mesogenic optical properties which have prospective utility in opto-electronic display devi ces 2 ~ 3 ~3"~
In Onited State6 P~tent ~imbers 4,694,066 4,755,574 and 4,762,912 liquid crystalline polymers are described which have pendant side chains which exhibit nonllnear optical susceptibility, in addition to mesogenic properties.
U.S. 4,792,208 discloses nonlinear optically responsive org~nic oompounds and.side chain polymers in which the molecular dipoles have an electron donor moiety linked through a conjugated ~ bonding system to an electron acceptor sulfonyl moiety. Japanese patent 88175834 discloses an acrylate polymer which has nitro~ethylhydroxyethylamino)azobenzene side chains.
Nonlinear optical proper~ies of organic and polymeric materials was the subject of a symposium sponsored by the ACS
division of Polymer Chemistry at the lBth meeting of the American Chemical Society, September 1982. Papers presented at the meeting are published in ~CS Symposium Series 233, American Chemical Society, Washington, D.C. 1983.
Thin films of organic or polymeric materials with large ~econd order nonlinearities in com~ination with silicon-based electronic circuitry have potential as systems for laser modulation and deflection, information control in optical circuitry, and the like.
Other novel processes occurring through third order nonlinearity ~uch as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have potential utility in such diverse fields as optical communications and integrated circuit fabrication.
.
~ - ~ ~__ 33~3 .. . .
Liquid crystalline side chain polymers which exhib~t nonlinear op~ical properties are suitable for application ~s a nonlinear optical component in optical light switch and light modulator devices. One disadvantage of a liquid crystalline side chain polymer optical medium is a loss of transmission efficiency due to light scattering by deviations from ideal meso~enic order~
There is continuing interest in the theory and practice of optically responsive polymers which are .
characterized by an oriented state o~ comb-like side chain struc~ures.
There is also an increasing research effort to develop new nonlinear optical ~rganic systems for prospective novel phenomena and devices adapted for laser frequency conver~ion, information control in optical circuitry, light valves and optical switches. The potential utility of organic materials with large second order and third order nonlinearlties for very high frequency appllcation contrasts with the bandwidth limitations of conventional inorganic electrooptic materials.
Accordingly, it is an object of this lnvention to provide optically re~ponsive monomers and polymers.
It is another object of this invention to provide polyvinyl copolymers having ~ide chains which exhibit nonlinear ptical response.
~ 'I
I I 2 ~
i I ., i It i5 a further object of this invention to provide optical waveguide media comprising a thin film of an amorphous li polymer with nonlinear optically-responsive pendant 6ide chains !I which can be uniaxially aligned by an external field.
¦l ~t~er objects and advantages of the present invention j shall become apparent from the accompanying description and examples.
.1 .
. _ ______ 1l 2~3l~ ~3 i ll DESCRIPTION OF THE INVENTION
. One or more objects of the present invention are l ~ ~
accompli~hed by the provision of a thin film optical waveguide medium comprising an amorphous polymer which exh~bits a second l order nonlinear optical susceptibility X of at least about ¦1 1 x 10 esu as measured at 1.34 ~m excitation wavelen~th, 'I and exhibits a light transmission optical loss of less than i about one decibel per centimeter.
In another embodiment this inYent~on provides a thin film optical waveguide medium comprising an nmorphous polymer which exhibits a second order nonlinear optical ~usceptibillty X of at leas~ about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter;
wherein the polymer is characteriæed by recurring monomeric ¦ units corresponding to the formula: ;
ll l ~P'~
i ¦ where P' is a polymer maln chain unit: S' is a pendant spacer group having a linear chain length of between about 2-12 atoms;
i M' is an organic structure which exhibits second order nonlinear optical susceptibility ~: and the polymer has a weight average molecular weight in the range between about 5000-200,00~
i 2[3~3~63 ~
In a preferred embodiment an invent~on thin film optical waveguide medium consists of a side chain polymer which is characterized by an external field-induced orientation and alignment of pendant side chains.
In the above represented side chain polymer formula, the main chain can be a structural type such as polyvinyl, polyoxyalkylene, polysiloxane, polycondensation, and the like.
A present invention polymer having pendant s;de chains which exhibit nonlinear optical susceptibility B is formed into a nonlinear optical medium, such as a transparent film or coating on a substrate. A polymer can be applied to a supporting substrate by conventional means, such as spin coating, spraying, Langmuir-Blodgett ~epositlon, and the like.
A film or coating fabricated with a present invention polymer initially exhibits third order nonllnear optical susceptibility. A thin film optical waveguide medium of the present invention after fabrication is subjected to an external field to orie~t and align uniaxially the polymer side chains.
In one method the polymer medium is heated close to or above the polymer glas~ transition temperature Tg, then an external field (e ., a DC eaectric field) is applied to the - 6 - .
~~ CEL-89-167 il POLYMERIC THIN FILM WAVE~:UIDE MEDIA
CR:)SS-REFEP~ENCE TO RELATED PATENT APPLICATlO~lS
_ _ _ __ __ _ ___ __ The present patent application has ~ubject matter i related to the disclosures of copending patent application ;I S.N. 14a,262, filed January 25, 1988 patent application ¦¦ S.N. 405,503, filed September 11~ 198~ patent application ¦ S.N. ~CEL-B8-116), filed ; and patent !¦ application S.N. (CEL-88-121), filed CI:C~O~
Polymers with a comb structure of pendant side chains are a new class of organic materials which exhibit interesting optical properties.
l Comb-like liquid crystalline polymers are described in ! Eur. Polym. J., 18, 651 (1982); Advanced Polymer Science, ,¦ Liquid Crystal Polymers II~III, Springer-Verlag, New York ~ (1984), pages 215-220: and in United States Patent Numbers i 4,293,435 and 4,6 1,3~8. ~be disclosed polymeric structures have ~een developed for their mesogenic optical properties which have prospective utility in opto-electronic display devi ces 2 ~ 3 ~3"~
In Onited State6 P~tent ~imbers 4,694,066 4,755,574 and 4,762,912 liquid crystalline polymers are described which have pendant side chains which exhibit nonllnear optical susceptibility, in addition to mesogenic properties.
U.S. 4,792,208 discloses nonlinear optically responsive org~nic oompounds and.side chain polymers in which the molecular dipoles have an electron donor moiety linked through a conjugated ~ bonding system to an electron acceptor sulfonyl moiety. Japanese patent 88175834 discloses an acrylate polymer which has nitro~ethylhydroxyethylamino)azobenzene side chains.
Nonlinear optical proper~ies of organic and polymeric materials was the subject of a symposium sponsored by the ACS
division of Polymer Chemistry at the lBth meeting of the American Chemical Society, September 1982. Papers presented at the meeting are published in ~CS Symposium Series 233, American Chemical Society, Washington, D.C. 1983.
Thin films of organic or polymeric materials with large ~econd order nonlinearities in com~ination with silicon-based electronic circuitry have potential as systems for laser modulation and deflection, information control in optical circuitry, and the like.
Other novel processes occurring through third order nonlinearity ~uch as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have potential utility in such diverse fields as optical communications and integrated circuit fabrication.
.
~ - ~ ~__ 33~3 .. . .
Liquid crystalline side chain polymers which exhib~t nonlinear op~ical properties are suitable for application ~s a nonlinear optical component in optical light switch and light modulator devices. One disadvantage of a liquid crystalline side chain polymer optical medium is a loss of transmission efficiency due to light scattering by deviations from ideal meso~enic order~
There is continuing interest in the theory and practice of optically responsive polymers which are .
characterized by an oriented state o~ comb-like side chain struc~ures.
There is also an increasing research effort to develop new nonlinear optical ~rganic systems for prospective novel phenomena and devices adapted for laser frequency conver~ion, information control in optical circuitry, light valves and optical switches. The potential utility of organic materials with large second order and third order nonlinearlties for very high frequency appllcation contrasts with the bandwidth limitations of conventional inorganic electrooptic materials.
Accordingly, it is an object of this lnvention to provide optically re~ponsive monomers and polymers.
It is another object of this invention to provide polyvinyl copolymers having ~ide chains which exhibit nonlinear ptical response.
~ 'I
I I 2 ~
i I ., i It i5 a further object of this invention to provide optical waveguide media comprising a thin film of an amorphous li polymer with nonlinear optically-responsive pendant 6ide chains !I which can be uniaxially aligned by an external field.
¦l ~t~er objects and advantages of the present invention j shall become apparent from the accompanying description and examples.
.1 .
. _ ______ 1l 2~3l~ ~3 i ll DESCRIPTION OF THE INVENTION
. One or more objects of the present invention are l ~ ~
accompli~hed by the provision of a thin film optical waveguide medium comprising an amorphous polymer which exh~bits a second l order nonlinear optical susceptibility X of at least about ¦1 1 x 10 esu as measured at 1.34 ~m excitation wavelen~th, 'I and exhibits a light transmission optical loss of less than i about one decibel per centimeter.
In another embodiment this inYent~on provides a thin film optical waveguide medium comprising an nmorphous polymer which exhibits a second order nonlinear optical ~usceptibillty X of at leas~ about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter;
wherein the polymer is characteriæed by recurring monomeric ¦ units corresponding to the formula: ;
ll l ~P'~
i ¦ where P' is a polymer maln chain unit: S' is a pendant spacer group having a linear chain length of between about 2-12 atoms;
i M' is an organic structure which exhibits second order nonlinear optical susceptibility ~: and the polymer has a weight average molecular weight in the range between about 5000-200,00~
i 2[3~3~63 ~
In a preferred embodiment an invent~on thin film optical waveguide medium consists of a side chain polymer which is characterized by an external field-induced orientation and alignment of pendant side chains.
In the above represented side chain polymer formula, the main chain can be a structural type such as polyvinyl, polyoxyalkylene, polysiloxane, polycondensation, and the like.
A present invention polymer having pendant s;de chains which exhibit nonlinear optical susceptibility B is formed into a nonlinear optical medium, such as a transparent film or coating on a substrate. A polymer can be applied to a supporting substrate by conventional means, such as spin coating, spraying, Langmuir-Blodgett ~epositlon, and the like.
A film or coating fabricated with a present invention polymer initially exhibits third order nonllnear optical susceptibility. A thin film optical waveguide medium of the present invention after fabrication is subjected to an external field to orie~t and align uniaxially the polymer side chains.
In one method the polymer medium is heated close to or above the polymer glas~ transition temperature Tg, then an external field (e ., a DC eaectric field) is applied to the - 6 - .
3 ~
.` ,, j I
!
medium of mobile polymer molecules to induce uniaxial molecular alignment of polymer side chains parallel to the applied field, and the medium is cooled while maintaîning the external field effect. I
By this method a present invention thin film optical waveguide medium has a stable uniaxial alignment of polymer side chains. Thæ poled optical medium exhibits a second order nonlinear optical susceptlbility X ). A present invention poled thin film optical medium is cap~ble of exhibiting a x(2) level of 1 x 10 8 esu or higher as measured at 1.34 ~m excitation wavelength.
The term ~electron-donating~ as employed herein refers to substituents which oontribute electron density to the ~-electron system when the conjugated electronic structure is polarized by the input of electromagnetic energy.
The term ~electron-withdrawing~ as employed herein refers to electronegat~ve organic substituents which attract electron density from the ~-electron system when the conjugated electron structure is polarized by the input of electromagnetic energy.
Illustrative of electron donating ~ubstituents are amino, alkylamino, dialkylamino, l-piperidino, l-piperazino, l-pyrrolidino, acylamino, hydroxyl, thiolo, alkylthio, arylthio, alkoxy, aryloxy, acyloxy, ,3,4 tetrahydrcguinolinyl, anù the like.
~ I
~ _ . ~_ 2 ~ ~s~
! I !
l l l ,! Illustrative of electron-withdrawing substituents are 'I nitro, cyano, trifluoromethyl, acyl, carboxy, alkanoyloxy, il aroyloxy, carboxamido, alkoxysulfonyl, aryloxysulfonyl, and structures such as -C~-C(CN)2, -C(CN)-C(CN12, -S02C~3, ~ ~ ~ X , and ~ ~ , where x is ~ CN, -~o~
!I The term ~external field" as employed herein refers to '.
¦¦ an electric, magnetic or mechanical stress fleld which is !11 applied to a substrate of mobile polymer molecules, to induce dipolar alignment ~f the polymer molecules and/or polymer side Il cha;ns parallel to the field.
'¦ The term ~amorphous~ as employed herein refers to a transparent polymeric optical medium which exhibits only short range translational and orientati~nal order of , internuclear distance vectors rij. Short range order refers to order in which there i~ preferred internuc}ear distances between nearest neighbor atoms as ~ccurs in a liquid. This is distinct from long range order, in which atoms lie on preferred jl sites within a repeating unit cell with both three dimensional j trans!at;onal and ~otational order as occurs in a crystalline ¦~ materirl. Tbis iY also distinct irom order in whi~h atoms ~, - a-.1 ,, ,1, , ~ ~3 ~ 3 .i~ G~ 3 ; ~ ~
, occupy preferred sites which repeat with long range translational and/or rotational order in less than three dimensions for ~oth translation and/or rotatiol as occurs in i liquid crystalline materials or plastic crystals.
Long range order requires repetition over sevecal unit cells. The number of unit cells determines the range of ordering. For crystals this repetition of unit cells is known as the crystallite size. Materials may possess long ranye 'i translational and/or rotational order even if the order is defined within crystallites or domains in which there is no ' order between the crystallites vr domains. For example, a crystalline powder has long range order as does an unoriented smectic liquid crystalline material. If the range of order j approaches one unit cell, short and long range order cannot be il, distinguished but become identical in this limit.
! Diffraction of X-rays from a material possessing short l range translational order consists of broad halos of scatt~ring ;I which cannot be indexed on a re~ular reciprocal lattice.
Materials with long range translational order exhibit broad or sharp diffraction depending upon the range of order, but in ~¦ this ca~e the ~catterin~ cannot be inde~ed on a regular ! reciprocal lattice ~n at least one direction.
!1 ., .
g .j .
. .
i jl Amorphous polymers display short range order and may be aligned so that there is preferred orientation. X-ray ~! scattering fr~m oriented amorphous materials show halos of ¦I scattering which are confined to arcs but cannot be indexed on !l a regular reciprocal lattice.
! Certain liquid crystalline materials such as nematic liquid crystals or nematic liquid crystalline polymers also ,' scatter X-rays into broad ~alos which do not occur along a ~1 . I
regular lattice. These materials may be oriented or ~j I
,j unoriented. AmorphoUs polymers may be distinguished from these ', liguid crystalline materials by their thermal behavior. Liquid ! crystalline materials display first or second order thermal phase transitions upon heating which may be observed by li calorimetry.
Amorphous polymers do not display thermal phase il transitions upon heating, but instead display a glass ,~
;' transition which may be observed by calorimetry.
',~ , 'I ~
- 10 - , I
Il !
. l .
., I
li !
.~
2 .~ q; ~ ~ l In another embodiment this invention provides a thin film optical waveguide medium comprising an amorphous polymer ¦~
which exhibits a second order nonlinear optical susceptibility X Of at least about 1 x 10 esu as measured at .1. 34 ~m excitation ~avelength, and exhihits a light transmission optical loss o~ less than about one dec~bel per centimeter;
wherein the polymer is characterized by recurring monomeric units corresponding to the formula: i where Pl is a maiD chain polyvinyl unit S' is a pendant spacer group having a linear chain length of between about 2-12 atoms; X is an electron-donating group: Y isl !
i , I
or ~ (CH=CH~
and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about ~40"-25C.
-__ ¦ ~ b~
l l i . ~ l The polymer corresponding to the above represented formula can be a homopolymer or a copolymer.
The recurring PV monomer uni~ in ~he above formula can be a polymerized radical of vinyl compounds such as acrylate, vinyl carboxylate, substituted arylvinyl~ and the like. When the invention polymer is a copolymer type, the PV monomer unit in the above formula is copolymerized with one or more vinyl mono~ers such as acrylate, vinyl halide, vinyl carboxylate, alkene, alkadiene, arylvinyl, and the like. The monomer species are exemplified by methacrylat~, vinyl chloride, vinyl acetate, ethylene, propylene, isobutylene, l-butene, isoprene, styrene, and the like.
In another embodiment this invention provides a thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X Of at least about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter;
wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
R R
CH - C~ 2 I =0 C02R
- ( C~2 ) ,,-X-Y- ( Z ) 1- 3 ., where m aDd m are iDtegers which total at le~st 10 R is " hydrogen or a Cl-C4 alkyl n is an integer having a value of 2-8; X is oxygen, sulfur or an amino or cycloamino group, R is a Cl-C12 alkyl or cycloalkyl 9roup; Y is .' or ~ ~CH=CH) ~¦ aDd Z i D electron-withdrawing group and the polymer has a glass transition temperature.in the range between about 50-200C.
Illustrative of C1-C4 alkyl, amino, cycloamino, Cl-C12 alkyl and cycloalkyl groups are methyl, ethyl, ¦
propyl, butyl, 2-butyl, pentyl, octyl, decyl, -Nff , -NR-, ¦
~ N-, -N ~ -, ~r, cyclopentyl, cyclohexyl, and the like.
j In a preferred embodiment this invention provides a thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order ~onlinear optical susceptibility x(2) of at least about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per I centimeter; wherein the polymer is characterized by recurring monoTneric units corresponding to the formula: ¦
_ 13 _ , . I , .. ~__ ' ~
1 I !
. R R
i + 2 1 ~ f 2 l C=O CQ2-R ' ~
c~2~2 4 L ~ ~CH=CH) ~ (NO2)l_3 i where m and ml are in~egers which total at least lO, R is hydrogen or Cl-C4 alkyl; ~ is -NRl- or -Q\__/N-; Rl is hydrogen or a Cl-C4 alkyl group Q is nitrogen or a -CH-radical; R is a Cl-C12 alkyl or cycloalkyl group; the m monomer comprises between about ~0-70 mole percent of the total mo~omers; and the poly~er has a glass transition temperature in the range between about 50-~OO~C.
In another embodiment this invention provides a thin film optical waveguide medium comprising an am~rphous polymer which exhibits a second order nonlinear optical:susceptibility x(2) of at least about 1 x 10 8 esu as measured at 1.34 ~m excitation wavelength, and exhlbits a light transmission optical loss of less than about one decibel per centimeter:
~herein the polymer is characterizsd by recurring monomeric units corresponding to the formula:
_ 14 _ . ~_ 2 ~ '~, 3 ~ ~ 3 1' ~
P
X-Y-Z
where CP is a main chain condensatlon polymer unit: and S', X, Y and z are a previously defined.
In another embodiment this invention provides a thin film optical waveguide med~um comprising amorphous p~lymer which exhibits a second order nonlinear optical susceptibility X of at least about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter wherein the p~lymer is characterized by recurring monomeric units corresponding to the formula:
!
s~
I S' X-Y-Z
where PS is a main chain polysiloxane unit and S', X, Y and Z
are as previously defined.
Illustrative of a polysiloxane is a structure characterized by recurring monomeric units corresponding to the formula:
A ~ ~ .
I!
I!
R
' I ~Si -0 i 1, . i !
j where R is a Cl-C1D hydrocarbyl substituent; and S', X, Y
~1 and Z are as previc>usly 13efined. Illustrative of hydrocarbyl groups are methyl, cyclohexyl and phenyl.
A present inVentiQn thin film optical waveguiding medium of an amorphous polymer has particular advantage in ! comparison with a medium of a liquid crystalline polymer. A
present invention optical medium exhibits exceptional optical transparency, whlle a liquid crystalline medium e~hibits a I light scattering effect b~cause ~f deviation ~rom ideal il crystalline order. The efficiency of light transmission in an ! optical waveguide is diminished by light scattering.
In another embodiment this invention provides a ~¦ waveguide medium for optical modulation of light which " co~prises:
a. a thin film optical waveguide medium comprising an amorphous polymer which exhibit~ a second order nonlinear , optical susceptibility X of at least about 1 x 10 esu ,l as measured at 1.34 ~m excitation wavelength, and exhibits a il light transmission optical loss of less than about one decibel !l per centimeter; and .
- 16 ~
, il .
~3'~3 1i b. an upper claddin~ layer and a lower cladding layer, each of which consists of a transparent ~rganic medium which has a lower index of refraction than the waveguiding thin film component.
~1 .
'! In another embodi~ent this invention provides a thin 1' film waveguide electrooptic light modulator which consists of a ,l laminated assembly of substrates comprisiny:
a. a thin film optical wa~eguide medium comprising an amorphous poly~er which exhibits a second order nonlinear optical susceptibility X of at least about 1 x 10 esu ! as measured at 1.34 ~m excitation wavelength, and exhibits a ~¦ light transmission optical loss of less than about one decibel jl per centimeter:
b. upper and lower cladding layers, each of which jl consists of an amorphous polymer medium which has an index of refraction between about O.nOl-0.2 lower than the ~aveguiding Il thim film component, and which exhibits 6eGond order nonlinear 1 optical susceptibility X and c. electrodes which are positioned to apply an i electric field to the assembly o~ waveguiding thin film and cladding layers.
1! .
' - 17 - l l l l .j i l? .
!I 1l ij .
i ,.
! I ¦
~ ~ S~
, ;
1, i F~r many applications a thin film waveguide has a , single mode channel structure, s~ch as a two.channel ' directional coupling configuration.
For some device applications it ~s highly preferred I that an invention waveguide medium has a spatial peri~dic structure for phase matching of propagating funda~ental and I harmonic light waves. The soheren~e length R of the I periodic polymeric medium is defined by the equa~ion: ¦
il 1T .
c ¦ where ~ is the propagation constant difference which is equal o l O l)~ ~l is the fundamental requen and subscript zero denotes the zero-ordered mode in the waveguide. The periodic structure can be bidirectional in the form of alternating zones of uniaxially aligned polymer chains, with the alternating zones having opposite directional l! alignments.
An optical device containing a present invention thin film waveguide medium as a nonlinear optical csmponent can be a laser freauency converter, an optical interferometric waveguide ¦ gate, a wide-band electrooptical guided wave analog-to-digital converter, an optical parametric device, and the like, as desc~ibed in u.S. 4,775,215.
Il I
~ c3~3 I
The theory o~ nonlinear harmonic generation by . frequency modulation of coherent light is elaborated by A. F, Garito et al in Chapter 1, ~'Molecular Optics:~onlinear Optl.cal Properties Of Organic And Polymeric Crystal~^: ACS
~ Sy~.~osiu~ Series 233 (1983).
'~ ~s it is apparent from the foregoing description of `! the present inventio~ thin film waveguide and device jl embodiments, an essential aspect of the present invention is il the utilisation of an amorphous polyme~ as the thin film waveguiding nonlinear optical medium, to the ex~.-lusion of I liquid crystalline polymers which can be less efficient for the !¦ transmission of propagating light waves.
~i With respect to side chain polymers and copolymers for fabrication of thin ~ilm optical wavegui~e media, it is necessary to d~stinguish and select between closely related polymeric structures. ~s determined by steric effects, some ~! side chain polymers and copolymers are amorphous and some are ,1 liquid crystalline in properties. .
j These factors are illustrated by the following ! observations in connection with the relationship between polyrler structure and optical properties.
-- 19 _ 2 ~ 3 3 .~
~ ' I
f 3 l~ I. 2 2 n ~ ~ N~2 ~lq.W.~gOOO
i When n in formula I is 12, Differential Scanning Colorimetry ~DSC) indicates a T of 23C, a liquid crystalline melt phase, and a clearing temperature of 79~C.
When n in formula I is 6, D~C indicates a T of 45C~ a liquid crystalline me}t phase, and a clearing temperature of 67C. I
When n in formula I is 3, DSC indicates a T of 86C, and no liquid crystalline melt phase is evident.
II. 2 2 6 ~ CN'CH ~ No2 .W.= 1 ,000 I
ll I
!~
CH~ CH3 2 CH ~ 50/50 CC)2ch3 Il 2 2 6 ~ CH=CH ~ N0 M.W. ~10,000 The formula II homopolymer has a T of 68C, a liquid crystalline melt phasel and a clearing temperature of Il 14~C.
I I The formula III copolymer has a T ~f 65aC, and no liquid crystalline melt phase is evident.
The formulas II-III demonstrate that a side chain homopolymer which exhibits liquid crystalline properties can be ¦ transformed into a copolymer wh;c~ does not exhibit liquid ¦ crystalline properties. The homopolymer of formula II as a il thin film waveguide medium exhibits a light transmission i optical loss of greater than about one decibel per centimeter, and therefore is not suitable for purposes of the present . invention. The copolymer of formula II as a thin film waveguide medium exhibits a light transmission optical loss of .
i less than about one decibel per centimeter, and therefore is a ! qualified optical optical medium within the ~cope of the present invention embodiments ~ince it also exhibits a second . order nonlinear optical suscepti~ility of greater than 1 x 10 su when in a poled s state.
1~ _ L
; . ~,~*Y~'~
'i . I
d The following examples are further illustrative of the ' present invention. The ~pecific ingredients of polymer il synthesis and the waveguide component fabrication are presented ¦l as being typical, and various modifications can be derived in ¦ view of the foregoing disclosure within the scope of the invention .
1, .
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!
_ Z;~ _ ' ' l fi~ f ~
EXAMPLE I
; This Example illustrates the preparation of amorphous I
~i homopolymer and an isotropic copolymer (25~75).
¦I + CH -CH~ CH -CH-~- 25/75 " C-- ~ 2 C 1 1,~ , l-(C1~2)2-1;~CII-CII_C~I=CH~;;3N02 . 1.
. . ''.
I + CH -CH~ CH -CH } 25/75 i l C-O ~ 02C~3 O-(CH~)2-1 ~ CH~CH~CH=CH ~ CN
.
+ CH2-fH ~ ~ 2 C=O C2CH3 . . C~7 j ; 2 2 1 ~ CN~CE3-C~CH~ ~ =C(CN2)~
~ - 23 -. I
1~ 1 2 ~ c~
., I
'I .
: A. 4-~N 2-hydroxxet~ N-eth~lamino)benzaldehxde ~l ~o a three neck flask fitted with a mechanical stirrer, a thermometer, and a condenser, is ~dded 124 9 .1 (1 mole) o~ 4-fluorobenzaldehyde, 89.1 9 ll mole) of i 2-(N-ethylamino)ethanol, 138.2 g (1 mole) of anhydrous ! potassium carbonate, and dimethylsulfoxide. The mixture is heated at 95C for 3 hour~. After cooling to room temperature, l the solution is poured into a four-fold excess of ice water, ! and the solid product ls collected by f$1tration and recrystallized ~rom water.
'.1 .
B. 4-(N-2-acetoxye hyl-N-ethylamino)benzaldeh ~e To a stirred solution vf 193.2 g (1 mole) of j~ 4-~N-2 hydroxyethyl-N-ethylamino)benzaldehyde in !~ dichloromethane are added 153.1 9 .(.1.5 moles) of acetic ~! anhydride, 151.8 g ll.5 moles) of triethylamine, and 8.5 9 . ~7 mole ~) of 4-N,N-dimethylaminopyridine. The reaction ¦¦ mixture is stirred at room temperature for 16 hours. The ! product solution then is washed with cold 2N HCl followed by I satura~ed sodium bicarbonate, and the organic layer is filtered ~I through cotton/ and evaporated to dryness.
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~ C. ~ ~
:
!¦ To a solution of 235O3 9 ~1 mole) of ¦¦ 4-~N-2-acetoxyethyl-N-ethylamino~benzaldehyde in j¦ di~ethylformamide is added 738.7 9 (2.0 moles) of 1,3-dioxolan-2-ylmethyltributylphosphonium bromide in . di~ethylformamide, and the mixture is heated at 90C.
! Potassium t-butoxide t224.4 ~, 2.0 moles) is added, and heating is continued at 90C for 16 h~urs. After cooling to room . temper~ture, the solution is poured into a seven-fold excess of il water, the aqueous mixture is saturated with sodium chloride, !l and the solution is extracted with three portions of ether.
i! The combined organics are dried over 4A sieves, filtered Il through cotton, and evaporated. The crude reaction product is ¦¦ dissolved in 3M HCl, and the reaction is stirred at room ! temperature for 16 hours. After neutralization with saturated j~ sodium bicarbonate, the aqueous mixture is extracted with three portions of ether, and the combined organics are dried over 4A
il sieves, filtered through cotton, and evaporated to yield the ! cinnamaldehyde as an oil~ The product is purif~ed by :Elash ¦ chromatography (rilIca gel, 1:1 hexene:ethyl acetate).
Il .
- 2s -!
i I!
,~ D. 4-tN-2-hydroxyethyl-~1-ethylamino) 4'-nitro-1,4-diphenyl-I
;~ 1, 3-butadlene Il A solution of 21.9 9 ~0.1 mole) of ¦¦ 4-(N-2-hydroxyethyl-N-ethylamino)cinnamaldehyde~ 9.3 g ~1 mole) ¦¦ of aniline, and ~.19 g (1 mole ~) OI' toluenesulfonic acid in i toluene is heated at reflux for 17 hours with azeotropic removal of water. After the mixture is cooled to room temperatu~e, 17.2 9 (~.2 mole) of methacrylic acid and 18.1 9 ( 0~1 mole~ of 4-nitrophenylacetic acid are added to the solution, and the reaction ls stirred at room temperature ~or , 3 hours. The mixture then is heated at reflux for 16 hours.
¦! After cooling to room temperature~ the solid diphenylbutadiene precipitates from solution and is collected by filtration and purlfied y recrystallization from ethanol.
E. Synthesis ~f ac~ylate monomer 1, ~, A solution of 33.B g (0~1 mole) of 4-(N-2-hydroxyethyl-N-ethylamino)-4'-nitro-1,4-diphenyl-1,3-butadiene, 12.6 g (o.l mole) of acrylic anhydride, and 0.12 g (D.l mole %) of 4-N,N-dimethylaminopyridine ~n pyridine i~ heated at 80C until the reaction is complete. After cooling to room temperature, the 601ution is poured into water, and the solid monomer is collected by filtration and purified by recrystallization from ethanol. The monomer exhibits a B of 121 x 10 30 esu as measured at 1.92 ~m excitat~on wavelength.
ll Il ~;3 ~ q~
ll I ~
) i The acrylate monomer f~om above is dissolved in ! dimethylsulfoxide ~lD~ s~lution by weight~, and the solution is i degassed with argon for 15 minutes). AIBN (1 mole ~) is added lll to the mixture, and the resultant solution i8 degassed for an il additional 15 minutes. The reaction then is heated at 70C and iI run under argon for 1~ hou~s. After cooling to room temperature, the polymer is precipitated into methanol and collected by filtration. Purification is achieved by redissolving the polymer in methylene chloride and i precipitating into ace~one. The polymer has a T o~ about 200~C.
I
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G. Formation of 25,i75 copolymer The acrylate monomer ~9.5 9, 0.025 mole) and ~ethyl acrylate ( 6 . 46 g, 0 . 075 mole) are dissolved in dimethyls~lfoxide ~10~ solution by weight of sol~tes)! and the solution is de~assed ~or 15 minutes~ AIBN ~1 mole ~) is added to the mixture, and the solution is degassed for an additional 15 minutes. The reaction then is heated at 70C and run under argon overnight. After cooling to room temperature, the po'ymer i5 precipitated into methanol and collected by filtration. Puri~ication is achieved by redissolvin~ the polymer in tetrahydrofuran and precipitating into acetone. The recovered copolymer has a T of about 145C. A thin film of the copolymer exhibits a X of about 3 x 10 esu as measured at 1.~4 ~m excitation wavelength.
Following the same procedures as described above, three homopolymers and three copolymers are produced, except that in procedure D 4-nitrophenylacetic acid i8 replaced by 4-cyanophenylacetic acid, 4-dicyanovinylphenylacetic acid or 4-tricyanovinylphenylacet~c acid, respectively.
I
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I .
XAMPI,E~
This Example illustrates the preparation of amorphous 4-fN-( 2-methacroyloxyethyl)-N-methylamino]-2' ,4 '-dinitro~tilbene/
¦ methyl methacrylate copolymer (50/50). i IH3f H 3 2 fC~--f~
C~OC2CH3 N2 2 2 1 ~ CH=CH ~ 2 A ~
¦i A reactor is charged with 2-(methylamino)ethanol (134 9, 1.8 moles3, 4-fluorobenzaldehyde (74.4 g, 0.6 mole), ,¦ potassium carbonate (82.8 g, 0.6 mole) and dimethylsulfoxide ', (750 ml), and the mixture is heated at 95C for 72 hours. The I ,I product mixture is cooled and poured into three liters of Ice I water. The yellow ~olid tbat precipitates i~ filtered, washed ! with water, and dried in a vacuum oven, ~p 72C. The il 4-[N-t2-hydroxyethyl~-N-methyla~ino]benzaldehyde product is ¦¦ recrystallized from water a~ needle-like crystals.
9 _ I
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4-1N-~2-hydroxyethyl)-N-methylamino]benzaldehyde ~179 9, 1.0 mole) and toluene (1.2 liters) are charged to a reaction flask, and the reactor is purged with argon. The reaction is heated to reflux under argon, and water is removed with a Dean-Stark trap~
¦ Methanesulfonic acid (0.2 ml) is added to the refluxing solution~ and then aniline ~102 9, 1.1 moles) is added dropwise, and the heating is continued until about 18 ml o~ water is removed.
A yellow precipitate ~orms on cooling, and is , separated by filtration and dr~ed, mp lll.9~C.
C. Stilbene Alcohol . A reactor is charged with 2,4-dinitrophenylacetic acid . (45.23 g, 0.2 mole; Aldrich), toluene ~360 ml), and Schiff base l (50.9 g, 0.2 mole) as prepared above. The reaction mixture is !¦ stirred at room tempera~ure for one hour, then methacrylic acid ! ~ 34.4 q~ 0-4 ~ole) is added dropwise~ and the reactor contents l are heated at 75C for three hours and at 110C for two hours.
i On c~oling, the produc~ separates as greenish 1¦ cryctals, p 196--189'C.
l ., ~30 ~
~3~3~33 Ii D. ~crylate ~onomer ! A reactor is charged with s~ilbene alcohol (24 g, , 0.07 mole) as prepared above, pyridine (240 ml) and ¦¦ dimethylaminopyridine catalyst (1.71 9, 0.014 mole). The ¦ react~r contents are heated to 75C, and methacrylic anhydride ' (~9 ml, 0.1~5 mole) is added, and the reaction i~ conducted at 75C for 20 ho~rs.
,l ~he product mixture is cooled, and poured into 750 ml j¦ of water. The resultant black crystalline precipitate is !~ recovered by filtration and dried at 50C in a vac~um oven, ¦I mp 122~-125C. The chemical structure of the product is j' consistent with a NMR spectral analysis. Recrystalli~ation of !I the product from ethyl acetate/ethanol (3.2/1) yields shiny blach crystals, mp 125--126'C.
II
.1 i!
i l `I _ 31 _ il .
, , E Copol~er (50/~0) I A reactor is charged with 4.11 g 10.01 m~le) of j acrylate mono~er as prepared above and dimethylsulfoxide ;~ ~41 ml), and dry argon gas is bubbled into the solution. The ¦! reactor then is charged with methyl methacrylate (1.0 ml, Il 0.01 mole) and azodiisobutyronitrile ~33 mg) under an argon ,~ purge. ~he reaction mixture is heated at 70C ~or 48 hours to i form copolymer product.
The product mixture is poured into a S00 ml volume of ' methanol to precipitate the copolymer. The copolymer is 'l collected, then dissolved in tetrahydrofuran and reprec;pitated in a volume of methanol.
The glass transition temperature (T ) is 134~C, and the weight average molecular weight is about 9000, as ~¦ determined by size exclusion chromatography using Zorbax-PS
! bimodal columns with tetrahydrofuran as the mobile phase.
The copolymer is soluble in acetone, tetrahydrofuran or N-methylpyrrolidine, and insoluble in ethanol or toluene.
A thin film of the copolymer exhibits a X( ) ~f about 3.2 x 10 esu as measured at 1.34 ~m excitatioll ;
wavelength.
'I .
, EY.A~PLE I I I
This Example illustrates the preparation of an amorphous copolymer (5V/50).
.
~ ! l H3 t H3 {--CH2-C~CH~-C~ 50/50 C=O C02C~13 1,2,3,4-Tetrahydroguinoline tO.5 mole), 2-brom~-1-ethanol (2.5 moles), 250-500 ml of methanol and sodium carbonate (0.2S mole) are ad~ed to a flask fitted with a mechanical stirrer and condenser. The mixture is warmed to ! 80C for 16 hours, cooled to room temperature, and filtered to ;, remove the solids. The fi}trate is extracted with ether, and the ether is removed by rotary evaporation. The residue is ; vacuum distilled and separated into two frac~ions The ~irst ' fraction is excess bro~oethanol (51D-53~C, ,~ 0.8 mm ~g). The second fraction is 1-(2-hydroxyethyl)-1,2,3,4-tetrahydroquinoline l110-120C, 0.4 mm ~9~, in a ! ~% yield-_ 3 3 . !
l !
.~ f~
. i , l~ 4-Nitroaniline (0.25 mole) is added to an aqueous ,I solution of hydrochloric acid ~10~ v/v) which has been cooled il to 0C in an ice bath. Acetic acid (300 ml) is added to l! increase the solubility of the aniline. One equivalent of ¦¦ sodium nitrite is added to the aniline solut~on, while keeping the temperature below 10C.
I The l-t2-hydroxyethyl)-1,2,3,4-tetrahydroquinoline i (0.25 mole) is added directly to the dia~onium salt solution li and kept below 10C. The pH is adjusted to 4 by adding sodium acetate. The ice bath is removed and the mixture is stirred for 3 hours at room temperature. The 1-(2-hydroxyethyl)-6-~i (4'-nitrophenylazo)-1,2,3,4-tetrahydrOqUinOline is precipitated i into water, isolated, and washed with water. The yield is 60%.
! The l-t~-hydroxyethyl)-6-(4'-nitrophenylazo)-1,2,3,4-tetrahydroquinoline product (0.1~ mole), dimethylaminopyridine (0.03 mole) and toluene are added to a dried flask fitted with Ij an addition funnel, nitrogen hubbler, thermometerr and !j mechanical stirrer. The mixture under nitr~gen is warmed to 75C in a thermostated oil bath. Acrylic anhydride ~0.38 mole) which has been previously distilled is added slowly via the i addition funnel. The solution is kept at 75C for 16 hours.
The solution is cooled to room t~mperature and washed with aqueous sodium hydride. The toluene solution is dried over magnesium sulfate. The monomer is precipitated by the addition ! oi hexane t 60% yie~d).
Il _ 34 _ ~j . ~
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.
j The NLO-active monomer ~G.l mole, 39.44 9) is copolymerized with methyl methacrylate (0.1 mole) in 500 ml dried and purified dimethylsulfoxide with one mole%
a~obis(isobutyronitrilel (AIBN) under nitrogen. The monomers, Il solvent, and AI~N initiator are added to a round bottom flask, ,I covered with a septum, and degassed by bubbling nitrogen for ;~ 15 minutes. The nitrogen is changed t~ ~ sparge and the flask is warmed to 75C, and a positive nitrogen pressure is maintained in the flask. The monomers are polymerized for 12 hours at 75C. The copolymer product is precipitated into j methanol and isolated by filtration (90% conversion~.
j, The copolymer has a T of about 112C, and exhibits ¦ a ~ of about 180 x 10 esu as measured at 1.34 ~m excitation wavelength. A thin film of the copolymer exhibits a X f about 3 X 10 esu as measured at 1.34 ~m i excitation wavelength.
"
~l - 35 -!i ~l l I.j ~ ~ 3 ~
jl EXAMPLE I v 'This Example illustrates the construction and operation of an optical frequency converting waveguide module utilizing a present invention thin film optical waveguide medium.
A silicon dioxide-coated silicon wafer with a grating ! electrode is constructed by means of the following fabrication ¦! procedures.
A commercially available silicon dioxide-coated silicon wafer is placed in a Varian electron beam vacuum deposition system. A 0.1 ~m layer of 99.999% purity a:Luminum is deposited on the wafer.
AZ-1518 positive photoresis~ (Hoechst) is spin coated on the aluminum-c~ated wafer with a Solitec model 5100 coater~ ¦
A 1.5 ~m photoresist coating is achieved by spinning at 5000 rpm ¦
for 30 seconds. The photoresist coating is dried in a vacuum oven at 90C for 30 minutes.
~ he photoresist coating is patterned by placing the ¦! wafer in contact with a mask of the desired config~ration in a j! Xarl Suss model MJB3 mask aligner, and exposing the masked coating t~ 405 ~m radiation (70 mJ/cm~
The mask is removed, and a thin piece of silicon (1 cm x 2 cm) is placed on the surface of the patterned photoresist as a protective shield, and the combination is exposed to 70 m~/cm~ of 405 ~m radiation. The patterned il - 36 _ 'i ' i ' '2 ~ 3 !
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photoresist is deve1oped ~ith AZ Developer in water (1:1) over a !
period of 60 seconds, and the developing cycle is terminated by washing with deionized water.
i The photoresist-coating of ~he wafer is baked in a jl vacuum oven at 120C for 45 minutes. The ~exposed al~minum pattern is etched with type A et~hant (Transene Corp.) at 50C
~' for 20 seconds, and the etched surface is rinsed with d~eionized ,! water.
j~ The aluminum grating electrode surface of the wafer ,j then is covered with a 1.5 ym cladding layer of 20~ polyvinyl ,~ alcohol (75% hydrolyzed) in water by spin-coating at 5000 rpm j¦ for 30 seconds, and the cladding layer is dried in a vacuum oven Il at 110C ~or two hours.
~, , ~¦ A nonlinear optically active organic layer of 1.65 ~m , thickness is spin-coated on the cladding layer at 3000 rpm. The !
I! spin-coating medium is a 20% solution of an isotropic copolymer ~! ~50/50) of methyl methacrylate/4-(methacryloyloxy-2-hexoxy)-4'-nitrostilbene in trichl~ropropane. The organic layer is dried in a vacuum oven at 160C for one hour.
,i ~n upper cladding layer o~ 1.5 ~m thickness is added by spin-coating a medlum of polysiloxane (GR-651-~, 0wens-Illinois ~ Inc., 25~ solids in l-butanol) a~ 3500 rpm for 30 seconds. The jl cladding layer is dried in a vacuum oven at 110C for 35 minutes. A 0.055 ~m coatlng of aluminum is deposited as an ,l electrode layer on the upper cladding layer~
.1 '.
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The fabricated waveguide is placed in a Mettler hot , stage, and the unit is raised to 90C at 1C/min. A DC field of 70V~m is applied across the waveguiding organic layer for ten ~? minutes h~ means of the electrodes. The electric field is ~,aintained while the waveguide sample is cooled to r~om temperature at l~C/min. The X nonlinear optical response of the waveguiding medium is 1 ~ 10 esu as measured at 4 ~Im exci tation wavelength.
' The waveguide structure is cleaved at opposite ends to provide two sharp faces to ~ouple light in and out of the , waveguiding organic layer.
Cylindrical lenses are employed to focus and couple i 1. 34 radiation ( O. 01 mJ, 10 nsec wide pulse) into the Il waveguide The waveguide is situated on a rotation ~tage, and ! phase-matched second harmonic generati~n is observed when the l waveguide is rotated until the periodicity satisfies the value ! for phase-matching. Under the described operating conditions, a 0.5-1% amount of the fundamental beam is converted into observed ~! second harmonic radiation.
I A nonlinear optical response occurs in the fabricated ¦j device upon excitation with ~M~ radiation. As the sample is j¦ rotated, the grating ma~ches the required periodicity for !I phase-matching and the second harmonic signal increases, demonstrati~g that phase-matched interaction has occurred I between the fundamental mode TM and its harmonic TM2~ i o o li _ 38 _ i i ~ V tJ
EY.A~PLE V
This Example i~lustrates the construction and operation i of a polarization-insensitive waveguide electrooptic modulator Il utilizing a present invention thin film opti~al waveguide medium.
iA commercially available silicon dioxide-coated silicon wafer is placed in a Varian electron beam vacuum deposition system. A n.l ~m layer of 99.999% purity gold is deposited on the wafer. I
AZ-151~ positive photoresist (Hoechst) is spin-coated on the alu~inum-coated wafer with a Solltec model 5100 coater.
j A 1.5 ~m photoresist coating is achieved by spinning at 5000 rpm for 30 seconds. The photoresist coating is dried ;n a vacuum ! oven at gaoc for 30 minutes.
I The photoresist coating is patterned in the form of ¦ lower electrode by placing the wafer in contact with a mask of i' the desired configuration in a Karl Suss model MJB3 mask i, aligner, and exposing the marked coating to 405 ~m radiation t120 mJ~cm2).
The mask is removed, and the patterned photoresist is developed with AZ-400k Developer in water (1:1) over a period of ~
j 45 seconds, and the developing cycle is terminated by washin~ I
¦I with deionized water~
!i The photoresist-coating of the wafer is baked in a ! vacuum oven at 120C for 30 minutes. The exposed aluminum pattern is etched with type ~ etchant at 50~C for 2a seconds, and the etched surface i~ rinsed with deionized water.
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The aluminum electrode surface o~ the wafer is covered with a thin llO00 A~ protective polysiloxane layer, fol~owed by a 1.5 ~m lower ~rganic cladding layer of a 20~ solution of an amorphous copolymer (40/60~ of methyl methacrylate/
4-mett1acryloyloxy-2-ethoxy-4'-nitrostilbene in trichl~ropropane by spin-coating at 3000 rpm for 30 seconds, and the cladding layer is dried in a vacuum oven at 160C for one hour~ The organic polymer has a molecular weight of about 30,000, and the cladding layer has a refractive index of 1.42.
The wafer then is exposed tv reactive lon etching for S seconds to improve surface adhesion to ~ubsequent layers. The etching conditions are five standard cubic.centimeters per minute of 2 flowing at lS mtorr pressure, with 30 watts~6 diameter platten of 13.56 MHz r.f. power.
A nonlinear optically active thin film waveguide layer of 1.65 ~m thickness is spin-coated on the lower cladding layer at 3C00 rpm. The spin-coating medium i~ a 20% ~olution of an isotropic copolymer (50/50) of methyl methacrylate/
4-(methacryloyloxy-2-ethoxy)-4'- nitrostilbene in trichloropropane, The organic layer is dried in a vacuum oven at 160C for one hour. The organic polymer has a molecular weight of about 30,000~ and the thin film has a refractive index o~ 1.49 ,, .
I _ 40 _ !
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A photoresist layer of Az-l5lB is spin-coated on the , thin film waveguide layer at 4000 rpm, and the layer is exposed I to 405 ~m radiativn (120 mJ/cm ). A 0.2 ~m layer of aluminum il is deposited on the photoresist layer. The aluminum layer is '! coated ~ith a photoresist layer, and the layer i~ patterned in ! the form of a Mach-Zehnder interferometric waveguide. The waveguide width is 5 ~m. The Y junction channels separate and , recombine at a full angle of G.3 degrees.
i¦ The upper surface of the waveguide structure is exposed to reactive ion etching for 15 minutes under oxygen plasma conditions as previo~sly described, to remove the m~ltilayers down to the bottom silicon substrate, except for the photoresist coated pattern. The etching cycles ~lso rem3ve the pho~oresist ¦ coating from the aluminum pattern.
The aluminum and lower photoresist layers are removed ! by immersion of the waveguide ~tructure in AZ-400k developer for one minute.
I The substrate and the upper surface multilayer rib j pattern are spin-coated with an upper organic claddin~ layer in the same manner as described above for the lower cladding layer.
Il A 0.1 ~m layar of aluminum is deposited on the upper ! organic cladding layer, and follow~ng the pattern procedures described above an upper electrode is formed on the ~irst channel, ~nd a pair of parallel electrodes are formed on the ~! second channel.
~J3 i i i il . I
The waveg~ide structure is cleaved at opposite ends to provide two sharp faces to couple light in and out of the j waveguiding thin film and cladding assembly.
!, Molecular orientation of the two polymeric waveguide ¦1 assembly sections between the two sets o electrodes respectively is accomplished by application of applied electric fields ~y the sets of electrodes.
il The fabricated waveguide device is placed in a Mettler Il hot stage, and the unit is raised to 90C at 1C/min. A ~C
i! field of 70 V~m and an AC voltage of 5 volts sine (10,000 t) is ~; i applied to one set o~ eleotrodes, and a variable DC voltage and ~¦ an AC voltage of 5 volts sine (lO,ODO t) are applied to the other set of electrodes.
¦ Ob~ective lenses ~lOXI are employed to focus and couple ¦1 1.34 radiation ~m (100 mW continuous wave) into the Mach-zehnder Ij waveguide. The output of the waveguide is passed through a lOX
!! microscope objective, a polarization beam splitter, and then ,¦ into two opt;cal detectors. The detector signals are transmitted to two lock-in amplifiers.
Both amplifiers are tuned for a signal at iO,OOO Herz, and the variable DC ~oltage to the first set of electrodes is il adjusted until the signals in the two amplifiers are identical.
l The waveguide unit is held at 90C for 20 minutes under I the adjusted applied fields, and the applied fields are ¦~ maintained while the waveguide unit is cooled to room temperature at 1Ctminute.
i !
! .
~3~&33 1 During operation of the waveguide, the effected light ~! modulation is polarization-insensitive because the voltages '¦ applied to the two sets of electrodes are balanced to achieve '¦ equal phase ~odulation of the TE and TM modes of transmitted Il light.
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medium of mobile polymer molecules to induce uniaxial molecular alignment of polymer side chains parallel to the applied field, and the medium is cooled while maintaîning the external field effect. I
By this method a present invention thin film optical waveguide medium has a stable uniaxial alignment of polymer side chains. Thæ poled optical medium exhibits a second order nonlinear optical susceptlbility X ). A present invention poled thin film optical medium is cap~ble of exhibiting a x(2) level of 1 x 10 8 esu or higher as measured at 1.34 ~m excitation wavelength.
The term ~electron-donating~ as employed herein refers to substituents which oontribute electron density to the ~-electron system when the conjugated electronic structure is polarized by the input of electromagnetic energy.
The term ~electron-withdrawing~ as employed herein refers to electronegat~ve organic substituents which attract electron density from the ~-electron system when the conjugated electron structure is polarized by the input of electromagnetic energy.
Illustrative of electron donating ~ubstituents are amino, alkylamino, dialkylamino, l-piperidino, l-piperazino, l-pyrrolidino, acylamino, hydroxyl, thiolo, alkylthio, arylthio, alkoxy, aryloxy, acyloxy, ,3,4 tetrahydrcguinolinyl, anù the like.
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l l l ,! Illustrative of electron-withdrawing substituents are 'I nitro, cyano, trifluoromethyl, acyl, carboxy, alkanoyloxy, il aroyloxy, carboxamido, alkoxysulfonyl, aryloxysulfonyl, and structures such as -C~-C(CN)2, -C(CN)-C(CN12, -S02C~3, ~ ~ ~ X , and ~ ~ , where x is ~ CN, -~o~
!I The term ~external field" as employed herein refers to '.
¦¦ an electric, magnetic or mechanical stress fleld which is !11 applied to a substrate of mobile polymer molecules, to induce dipolar alignment ~f the polymer molecules and/or polymer side Il cha;ns parallel to the field.
'¦ The term ~amorphous~ as employed herein refers to a transparent polymeric optical medium which exhibits only short range translational and orientati~nal order of , internuclear distance vectors rij. Short range order refers to order in which there i~ preferred internuc}ear distances between nearest neighbor atoms as ~ccurs in a liquid. This is distinct from long range order, in which atoms lie on preferred jl sites within a repeating unit cell with both three dimensional j trans!at;onal and ~otational order as occurs in a crystalline ¦~ materirl. Tbis iY also distinct irom order in whi~h atoms ~, - a-.1 ,, ,1, , ~ ~3 ~ 3 .i~ G~ 3 ; ~ ~
, occupy preferred sites which repeat with long range translational and/or rotational order in less than three dimensions for ~oth translation and/or rotatiol as occurs in i liquid crystalline materials or plastic crystals.
Long range order requires repetition over sevecal unit cells. The number of unit cells determines the range of ordering. For crystals this repetition of unit cells is known as the crystallite size. Materials may possess long ranye 'i translational and/or rotational order even if the order is defined within crystallites or domains in which there is no ' order between the crystallites vr domains. For example, a crystalline powder has long range order as does an unoriented smectic liquid crystalline material. If the range of order j approaches one unit cell, short and long range order cannot be il, distinguished but become identical in this limit.
! Diffraction of X-rays from a material possessing short l range translational order consists of broad halos of scatt~ring ;I which cannot be indexed on a re~ular reciprocal lattice.
Materials with long range translational order exhibit broad or sharp diffraction depending upon the range of order, but in ~¦ this ca~e the ~catterin~ cannot be inde~ed on a regular ! reciprocal lattice ~n at least one direction.
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i jl Amorphous polymers display short range order and may be aligned so that there is preferred orientation. X-ray ~! scattering fr~m oriented amorphous materials show halos of ¦I scattering which are confined to arcs but cannot be indexed on !l a regular reciprocal lattice.
! Certain liquid crystalline materials such as nematic liquid crystals or nematic liquid crystalline polymers also ,' scatter X-rays into broad ~alos which do not occur along a ~1 . I
regular lattice. These materials may be oriented or ~j I
,j unoriented. AmorphoUs polymers may be distinguished from these ', liguid crystalline materials by their thermal behavior. Liquid ! crystalline materials display first or second order thermal phase transitions upon heating which may be observed by li calorimetry.
Amorphous polymers do not display thermal phase il transitions upon heating, but instead display a glass ,~
;' transition which may be observed by calorimetry.
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2 .~ q; ~ ~ l In another embodiment this invention provides a thin film optical waveguide medium comprising an amorphous polymer ¦~
which exhibits a second order nonlinear optical susceptibility X Of at least about 1 x 10 esu as measured at .1. 34 ~m excitation ~avelength, and exhihits a light transmission optical loss o~ less than about one dec~bel per centimeter;
wherein the polymer is characterized by recurring monomeric units corresponding to the formula: i where Pl is a maiD chain polyvinyl unit S' is a pendant spacer group having a linear chain length of between about 2-12 atoms; X is an electron-donating group: Y isl !
i , I
or ~ (CH=CH~
and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about ~40"-25C.
-__ ¦ ~ b~
l l i . ~ l The polymer corresponding to the above represented formula can be a homopolymer or a copolymer.
The recurring PV monomer uni~ in ~he above formula can be a polymerized radical of vinyl compounds such as acrylate, vinyl carboxylate, substituted arylvinyl~ and the like. When the invention polymer is a copolymer type, the PV monomer unit in the above formula is copolymerized with one or more vinyl mono~ers such as acrylate, vinyl halide, vinyl carboxylate, alkene, alkadiene, arylvinyl, and the like. The monomer species are exemplified by methacrylat~, vinyl chloride, vinyl acetate, ethylene, propylene, isobutylene, l-butene, isoprene, styrene, and the like.
In another embodiment this invention provides a thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X Of at least about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter;
wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
R R
CH - C~ 2 I =0 C02R
- ( C~2 ) ,,-X-Y- ( Z ) 1- 3 ., where m aDd m are iDtegers which total at le~st 10 R is " hydrogen or a Cl-C4 alkyl n is an integer having a value of 2-8; X is oxygen, sulfur or an amino or cycloamino group, R is a Cl-C12 alkyl or cycloalkyl 9roup; Y is .' or ~ ~CH=CH) ~¦ aDd Z i D electron-withdrawing group and the polymer has a glass transition temperature.in the range between about 50-200C.
Illustrative of C1-C4 alkyl, amino, cycloamino, Cl-C12 alkyl and cycloalkyl groups are methyl, ethyl, ¦
propyl, butyl, 2-butyl, pentyl, octyl, decyl, -Nff , -NR-, ¦
~ N-, -N ~ -, ~r, cyclopentyl, cyclohexyl, and the like.
j In a preferred embodiment this invention provides a thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order ~onlinear optical susceptibility x(2) of at least about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per I centimeter; wherein the polymer is characterized by recurring monoTneric units corresponding to the formula: ¦
_ 13 _ , . I , .. ~__ ' ~
1 I !
. R R
i + 2 1 ~ f 2 l C=O CQ2-R ' ~
c~2~2 4 L ~ ~CH=CH) ~ (NO2)l_3 i where m and ml are in~egers which total at least lO, R is hydrogen or Cl-C4 alkyl; ~ is -NRl- or -Q\__/N-; Rl is hydrogen or a Cl-C4 alkyl group Q is nitrogen or a -CH-radical; R is a Cl-C12 alkyl or cycloalkyl group; the m monomer comprises between about ~0-70 mole percent of the total mo~omers; and the poly~er has a glass transition temperature in the range between about 50-~OO~C.
In another embodiment this invention provides a thin film optical waveguide medium comprising an am~rphous polymer which exhibits a second order nonlinear optical:susceptibility x(2) of at least about 1 x 10 8 esu as measured at 1.34 ~m excitation wavelength, and exhlbits a light transmission optical loss of less than about one decibel per centimeter:
~herein the polymer is characterizsd by recurring monomeric units corresponding to the formula:
_ 14 _ . ~_ 2 ~ '~, 3 ~ ~ 3 1' ~
P
X-Y-Z
where CP is a main chain condensatlon polymer unit: and S', X, Y and z are a previously defined.
In another embodiment this invention provides a thin film optical waveguide med~um comprising amorphous p~lymer which exhibits a second order nonlinear optical susceptibility X of at least about 1 x 10 esu as measured at 1.34 ~m excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter wherein the p~lymer is characterized by recurring monomeric units corresponding to the formula:
!
s~
I S' X-Y-Z
where PS is a main chain polysiloxane unit and S', X, Y and Z
are as previously defined.
Illustrative of a polysiloxane is a structure characterized by recurring monomeric units corresponding to the formula:
A ~ ~ .
I!
I!
R
' I ~Si -0 i 1, . i !
j where R is a Cl-C1D hydrocarbyl substituent; and S', X, Y
~1 and Z are as previc>usly 13efined. Illustrative of hydrocarbyl groups are methyl, cyclohexyl and phenyl.
A present inVentiQn thin film optical waveguiding medium of an amorphous polymer has particular advantage in ! comparison with a medium of a liquid crystalline polymer. A
present invention optical medium exhibits exceptional optical transparency, whlle a liquid crystalline medium e~hibits a I light scattering effect b~cause ~f deviation ~rom ideal il crystalline order. The efficiency of light transmission in an ! optical waveguide is diminished by light scattering.
In another embodiment this invention provides a ~¦ waveguide medium for optical modulation of light which " co~prises:
a. a thin film optical waveguide medium comprising an amorphous polymer which exhibit~ a second order nonlinear , optical susceptibility X of at least about 1 x 10 esu ,l as measured at 1.34 ~m excitation wavelength, and exhibits a il light transmission optical loss of less than about one decibel !l per centimeter; and .
- 16 ~
, il .
~3'~3 1i b. an upper claddin~ layer and a lower cladding layer, each of which consists of a transparent ~rganic medium which has a lower index of refraction than the waveguiding thin film component.
~1 .
'! In another embodi~ent this invention provides a thin 1' film waveguide electrooptic light modulator which consists of a ,l laminated assembly of substrates comprisiny:
a. a thin film optical wa~eguide medium comprising an amorphous poly~er which exhibits a second order nonlinear optical susceptibility X of at least about 1 x 10 esu ! as measured at 1.34 ~m excitation wavelength, and exhibits a ~¦ light transmission optical loss of less than about one decibel jl per centimeter:
b. upper and lower cladding layers, each of which jl consists of an amorphous polymer medium which has an index of refraction between about O.nOl-0.2 lower than the ~aveguiding Il thim film component, and which exhibits 6eGond order nonlinear 1 optical susceptibility X and c. electrodes which are positioned to apply an i electric field to the assembly o~ waveguiding thin film and cladding layers.
1! .
' - 17 - l l l l .j i l? .
!I 1l ij .
i ,.
! I ¦
~ ~ S~
, ;
1, i F~r many applications a thin film waveguide has a , single mode channel structure, s~ch as a two.channel ' directional coupling configuration.
For some device applications it ~s highly preferred I that an invention waveguide medium has a spatial peri~dic structure for phase matching of propagating funda~ental and I harmonic light waves. The soheren~e length R of the I periodic polymeric medium is defined by the equa~ion: ¦
il 1T .
c ¦ where ~ is the propagation constant difference which is equal o l O l)~ ~l is the fundamental requen and subscript zero denotes the zero-ordered mode in the waveguide. The periodic structure can be bidirectional in the form of alternating zones of uniaxially aligned polymer chains, with the alternating zones having opposite directional l! alignments.
An optical device containing a present invention thin film waveguide medium as a nonlinear optical csmponent can be a laser freauency converter, an optical interferometric waveguide ¦ gate, a wide-band electrooptical guided wave analog-to-digital converter, an optical parametric device, and the like, as desc~ibed in u.S. 4,775,215.
Il I
~ c3~3 I
The theory o~ nonlinear harmonic generation by . frequency modulation of coherent light is elaborated by A. F, Garito et al in Chapter 1, ~'Molecular Optics:~onlinear Optl.cal Properties Of Organic And Polymeric Crystal~^: ACS
~ Sy~.~osiu~ Series 233 (1983).
'~ ~s it is apparent from the foregoing description of `! the present inventio~ thin film waveguide and device jl embodiments, an essential aspect of the present invention is il the utilisation of an amorphous polyme~ as the thin film waveguiding nonlinear optical medium, to the ex~.-lusion of I liquid crystalline polymers which can be less efficient for the !¦ transmission of propagating light waves.
~i With respect to side chain polymers and copolymers for fabrication of thin ~ilm optical wavegui~e media, it is necessary to d~stinguish and select between closely related polymeric structures. ~s determined by steric effects, some ~! side chain polymers and copolymers are amorphous and some are ,1 liquid crystalline in properties. .
j These factors are illustrated by the following ! observations in connection with the relationship between polyrler structure and optical properties.
-- 19 _ 2 ~ 3 3 .~
~ ' I
f 3 l~ I. 2 2 n ~ ~ N~2 ~lq.W.~gOOO
i When n in formula I is 12, Differential Scanning Colorimetry ~DSC) indicates a T of 23C, a liquid crystalline melt phase, and a clearing temperature of 79~C.
When n in formula I is 6, D~C indicates a T of 45C~ a liquid crystalline me}t phase, and a clearing temperature of 67C. I
When n in formula I is 3, DSC indicates a T of 86C, and no liquid crystalline melt phase is evident.
II. 2 2 6 ~ CN'CH ~ No2 .W.= 1 ,000 I
ll I
!~
CH~ CH3 2 CH ~ 50/50 CC)2ch3 Il 2 2 6 ~ CH=CH ~ N0 M.W. ~10,000 The formula II homopolymer has a T of 68C, a liquid crystalline melt phasel and a clearing temperature of Il 14~C.
I I The formula III copolymer has a T ~f 65aC, and no liquid crystalline melt phase is evident.
The formulas II-III demonstrate that a side chain homopolymer which exhibits liquid crystalline properties can be ¦ transformed into a copolymer wh;c~ does not exhibit liquid ¦ crystalline properties. The homopolymer of formula II as a il thin film waveguide medium exhibits a light transmission i optical loss of greater than about one decibel per centimeter, and therefore is not suitable for purposes of the present . invention. The copolymer of formula II as a thin film waveguide medium exhibits a light transmission optical loss of .
i less than about one decibel per centimeter, and therefore is a ! qualified optical optical medium within the ~cope of the present invention embodiments ~ince it also exhibits a second . order nonlinear optical suscepti~ility of greater than 1 x 10 su when in a poled s state.
1~ _ L
; . ~,~*Y~'~
'i . I
d The following examples are further illustrative of the ' present invention. The ~pecific ingredients of polymer il synthesis and the waveguide component fabrication are presented ¦l as being typical, and various modifications can be derived in ¦ view of the foregoing disclosure within the scope of the invention .
1, .
!
!
.1 . i, ., , .
! I
!
_ Z;~ _ ' ' l fi~ f ~
EXAMPLE I
; This Example illustrates the preparation of amorphous I
~i homopolymer and an isotropic copolymer (25~75).
¦I + CH -CH~ CH -CH-~- 25/75 " C-- ~ 2 C 1 1,~ , l-(C1~2)2-1;~CII-CII_C~I=CH~;;3N02 . 1.
. . ''.
I + CH -CH~ CH -CH } 25/75 i l C-O ~ 02C~3 O-(CH~)2-1 ~ CH~CH~CH=CH ~ CN
.
+ CH2-fH ~ ~ 2 C=O C2CH3 . . C~7 j ; 2 2 1 ~ CN~CE3-C~CH~ ~ =C(CN2)~
~ - 23 -. I
1~ 1 2 ~ c~
., I
'I .
: A. 4-~N 2-hydroxxet~ N-eth~lamino)benzaldehxde ~l ~o a three neck flask fitted with a mechanical stirrer, a thermometer, and a condenser, is ~dded 124 9 .1 (1 mole) o~ 4-fluorobenzaldehyde, 89.1 9 ll mole) of i 2-(N-ethylamino)ethanol, 138.2 g (1 mole) of anhydrous ! potassium carbonate, and dimethylsulfoxide. The mixture is heated at 95C for 3 hour~. After cooling to room temperature, l the solution is poured into a four-fold excess of ice water, ! and the solid product ls collected by f$1tration and recrystallized ~rom water.
'.1 .
B. 4-(N-2-acetoxye hyl-N-ethylamino)benzaldeh ~e To a stirred solution vf 193.2 g (1 mole) of j~ 4-~N-2 hydroxyethyl-N-ethylamino)benzaldehyde in !~ dichloromethane are added 153.1 9 .(.1.5 moles) of acetic ~! anhydride, 151.8 g ll.5 moles) of triethylamine, and 8.5 9 . ~7 mole ~) of 4-N,N-dimethylaminopyridine. The reaction ¦¦ mixture is stirred at room temperature for 16 hours. The ! product solution then is washed with cold 2N HCl followed by I satura~ed sodium bicarbonate, and the organic layer is filtered ~I through cotton/ and evaporated to dryness.
~, I
~ - 2~ ~
ll :! !
. I .
!i ~J~
~ C. ~ ~
:
!¦ To a solution of 235O3 9 ~1 mole) of ¦¦ 4-~N-2-acetoxyethyl-N-ethylamino~benzaldehyde in j¦ di~ethylformamide is added 738.7 9 (2.0 moles) of 1,3-dioxolan-2-ylmethyltributylphosphonium bromide in . di~ethylformamide, and the mixture is heated at 90C.
! Potassium t-butoxide t224.4 ~, 2.0 moles) is added, and heating is continued at 90C for 16 h~urs. After cooling to room . temper~ture, the solution is poured into a seven-fold excess of il water, the aqueous mixture is saturated with sodium chloride, !l and the solution is extracted with three portions of ether.
i! The combined organics are dried over 4A sieves, filtered Il through cotton, and evaporated. The crude reaction product is ¦¦ dissolved in 3M HCl, and the reaction is stirred at room ! temperature for 16 hours. After neutralization with saturated j~ sodium bicarbonate, the aqueous mixture is extracted with three portions of ether, and the combined organics are dried over 4A
il sieves, filtered through cotton, and evaporated to yield the ! cinnamaldehyde as an oil~ The product is purif~ed by :Elash ¦ chromatography (rilIca gel, 1:1 hexene:ethyl acetate).
Il .
- 2s -!
i I!
,~ D. 4-tN-2-hydroxyethyl-~1-ethylamino) 4'-nitro-1,4-diphenyl-I
;~ 1, 3-butadlene Il A solution of 21.9 9 ~0.1 mole) of ¦¦ 4-(N-2-hydroxyethyl-N-ethylamino)cinnamaldehyde~ 9.3 g ~1 mole) ¦¦ of aniline, and ~.19 g (1 mole ~) OI' toluenesulfonic acid in i toluene is heated at reflux for 17 hours with azeotropic removal of water. After the mixture is cooled to room temperatu~e, 17.2 9 (~.2 mole) of methacrylic acid and 18.1 9 ( 0~1 mole~ of 4-nitrophenylacetic acid are added to the solution, and the reaction ls stirred at room temperature ~or , 3 hours. The mixture then is heated at reflux for 16 hours.
¦! After cooling to room temperature~ the solid diphenylbutadiene precipitates from solution and is collected by filtration and purlfied y recrystallization from ethanol.
E. Synthesis ~f ac~ylate monomer 1, ~, A solution of 33.B g (0~1 mole) of 4-(N-2-hydroxyethyl-N-ethylamino)-4'-nitro-1,4-diphenyl-1,3-butadiene, 12.6 g (o.l mole) of acrylic anhydride, and 0.12 g (D.l mole %) of 4-N,N-dimethylaminopyridine ~n pyridine i~ heated at 80C until the reaction is complete. After cooling to room temperature, the 601ution is poured into water, and the solid monomer is collected by filtration and purified by recrystallization from ethanol. The monomer exhibits a B of 121 x 10 30 esu as measured at 1.92 ~m excitat~on wavelength.
ll Il ~;3 ~ q~
ll I ~
) i The acrylate monomer f~om above is dissolved in ! dimethylsulfoxide ~lD~ s~lution by weight~, and the solution is i degassed with argon for 15 minutes). AIBN (1 mole ~) is added lll to the mixture, and the resultant solution i8 degassed for an il additional 15 minutes. The reaction then is heated at 70C and iI run under argon for 1~ hou~s. After cooling to room temperature, the polymer is precipitated into methanol and collected by filtration. Purification is achieved by redissolving the polymer in methylene chloride and i precipitating into ace~one. The polymer has a T o~ about 200~C.
I
j I
!l . ~ , , I
G. Formation of 25,i75 copolymer The acrylate monomer ~9.5 9, 0.025 mole) and ~ethyl acrylate ( 6 . 46 g, 0 . 075 mole) are dissolved in dimethyls~lfoxide ~10~ solution by weight of sol~tes)! and the solution is de~assed ~or 15 minutes~ AIBN ~1 mole ~) is added to the mixture, and the solution is degassed for an additional 15 minutes. The reaction then is heated at 70C and run under argon overnight. After cooling to room temperature, the po'ymer i5 precipitated into methanol and collected by filtration. Puri~ication is achieved by redissolvin~ the polymer in tetrahydrofuran and precipitating into acetone. The recovered copolymer has a T of about 145C. A thin film of the copolymer exhibits a X of about 3 x 10 esu as measured at 1.~4 ~m excitation wavelength.
Following the same procedures as described above, three homopolymers and three copolymers are produced, except that in procedure D 4-nitrophenylacetic acid i8 replaced by 4-cyanophenylacetic acid, 4-dicyanovinylphenylacetic acid or 4-tricyanovinylphenylacet~c acid, respectively.
I
~ . __ !
I .
XAMPI,E~
This Example illustrates the preparation of amorphous 4-fN-( 2-methacroyloxyethyl)-N-methylamino]-2' ,4 '-dinitro~tilbene/
¦ methyl methacrylate copolymer (50/50). i IH3f H 3 2 fC~--f~
C~OC2CH3 N2 2 2 1 ~ CH=CH ~ 2 A ~
¦i A reactor is charged with 2-(methylamino)ethanol (134 9, 1.8 moles3, 4-fluorobenzaldehyde (74.4 g, 0.6 mole), ,¦ potassium carbonate (82.8 g, 0.6 mole) and dimethylsulfoxide ', (750 ml), and the mixture is heated at 95C for 72 hours. The I ,I product mixture is cooled and poured into three liters of Ice I water. The yellow ~olid tbat precipitates i~ filtered, washed ! with water, and dried in a vacuum oven, ~p 72C. The il 4-[N-t2-hydroxyethyl~-N-methyla~ino]benzaldehyde product is ¦¦ recrystallized from water a~ needle-like crystals.
9 _ I
I
2a."~As~
1 ., I
s~
4-1N-~2-hydroxyethyl)-N-methylamino]benzaldehyde ~179 9, 1.0 mole) and toluene (1.2 liters) are charged to a reaction flask, and the reactor is purged with argon. The reaction is heated to reflux under argon, and water is removed with a Dean-Stark trap~
¦ Methanesulfonic acid (0.2 ml) is added to the refluxing solution~ and then aniline ~102 9, 1.1 moles) is added dropwise, and the heating is continued until about 18 ml o~ water is removed.
A yellow precipitate ~orms on cooling, and is , separated by filtration and dr~ed, mp lll.9~C.
C. Stilbene Alcohol . A reactor is charged with 2,4-dinitrophenylacetic acid . (45.23 g, 0.2 mole; Aldrich), toluene ~360 ml), and Schiff base l (50.9 g, 0.2 mole) as prepared above. The reaction mixture is !¦ stirred at room tempera~ure for one hour, then methacrylic acid ! ~ 34.4 q~ 0-4 ~ole) is added dropwise~ and the reactor contents l are heated at 75C for three hours and at 110C for two hours.
i On c~oling, the produc~ separates as greenish 1¦ cryctals, p 196--189'C.
l ., ~30 ~
~3~3~33 Ii D. ~crylate ~onomer ! A reactor is charged with s~ilbene alcohol (24 g, , 0.07 mole) as prepared above, pyridine (240 ml) and ¦¦ dimethylaminopyridine catalyst (1.71 9, 0.014 mole). The ¦ react~r contents are heated to 75C, and methacrylic anhydride ' (~9 ml, 0.1~5 mole) is added, and the reaction i~ conducted at 75C for 20 ho~rs.
,l ~he product mixture is cooled, and poured into 750 ml j¦ of water. The resultant black crystalline precipitate is !~ recovered by filtration and dried at 50C in a vac~um oven, ¦I mp 122~-125C. The chemical structure of the product is j' consistent with a NMR spectral analysis. Recrystalli~ation of !I the product from ethyl acetate/ethanol (3.2/1) yields shiny blach crystals, mp 125--126'C.
II
.1 i!
i l `I _ 31 _ il .
, , E Copol~er (50/~0) I A reactor is charged with 4.11 g 10.01 m~le) of j acrylate mono~er as prepared above and dimethylsulfoxide ;~ ~41 ml), and dry argon gas is bubbled into the solution. The ¦! reactor then is charged with methyl methacrylate (1.0 ml, Il 0.01 mole) and azodiisobutyronitrile ~33 mg) under an argon ,~ purge. ~he reaction mixture is heated at 70C ~or 48 hours to i form copolymer product.
The product mixture is poured into a S00 ml volume of ' methanol to precipitate the copolymer. The copolymer is 'l collected, then dissolved in tetrahydrofuran and reprec;pitated in a volume of methanol.
The glass transition temperature (T ) is 134~C, and the weight average molecular weight is about 9000, as ~¦ determined by size exclusion chromatography using Zorbax-PS
! bimodal columns with tetrahydrofuran as the mobile phase.
The copolymer is soluble in acetone, tetrahydrofuran or N-methylpyrrolidine, and insoluble in ethanol or toluene.
A thin film of the copolymer exhibits a X( ) ~f about 3.2 x 10 esu as measured at 1.34 ~m excitatioll ;
wavelength.
'I .
, EY.A~PLE I I I
This Example illustrates the preparation of an amorphous copolymer (5V/50).
.
~ ! l H3 t H3 {--CH2-C~CH~-C~ 50/50 C=O C02C~13 1,2,3,4-Tetrahydroguinoline tO.5 mole), 2-brom~-1-ethanol (2.5 moles), 250-500 ml of methanol and sodium carbonate (0.2S mole) are ad~ed to a flask fitted with a mechanical stirrer and condenser. The mixture is warmed to ! 80C for 16 hours, cooled to room temperature, and filtered to ;, remove the solids. The fi}trate is extracted with ether, and the ether is removed by rotary evaporation. The residue is ; vacuum distilled and separated into two frac~ions The ~irst ' fraction is excess bro~oethanol (51D-53~C, ,~ 0.8 mm ~g). The second fraction is 1-(2-hydroxyethyl)-1,2,3,4-tetrahydroquinoline l110-120C, 0.4 mm ~9~, in a ! ~% yield-_ 3 3 . !
l !
.~ f~
. i , l~ 4-Nitroaniline (0.25 mole) is added to an aqueous ,I solution of hydrochloric acid ~10~ v/v) which has been cooled il to 0C in an ice bath. Acetic acid (300 ml) is added to l! increase the solubility of the aniline. One equivalent of ¦¦ sodium nitrite is added to the aniline solut~on, while keeping the temperature below 10C.
I The l-t2-hydroxyethyl)-1,2,3,4-tetrahydroquinoline i (0.25 mole) is added directly to the dia~onium salt solution li and kept below 10C. The pH is adjusted to 4 by adding sodium acetate. The ice bath is removed and the mixture is stirred for 3 hours at room temperature. The 1-(2-hydroxyethyl)-6-~i (4'-nitrophenylazo)-1,2,3,4-tetrahydrOqUinOline is precipitated i into water, isolated, and washed with water. The yield is 60%.
! The l-t~-hydroxyethyl)-6-(4'-nitrophenylazo)-1,2,3,4-tetrahydroquinoline product (0.1~ mole), dimethylaminopyridine (0.03 mole) and toluene are added to a dried flask fitted with Ij an addition funnel, nitrogen hubbler, thermometerr and !j mechanical stirrer. The mixture under nitr~gen is warmed to 75C in a thermostated oil bath. Acrylic anhydride ~0.38 mole) which has been previously distilled is added slowly via the i addition funnel. The solution is kept at 75C for 16 hours.
The solution is cooled to room t~mperature and washed with aqueous sodium hydride. The toluene solution is dried over magnesium sulfate. The monomer is precipitated by the addition ! oi hexane t 60% yie~d).
Il _ 34 _ ~j . ~
!
~3~
.
j The NLO-active monomer ~G.l mole, 39.44 9) is copolymerized with methyl methacrylate (0.1 mole) in 500 ml dried and purified dimethylsulfoxide with one mole%
a~obis(isobutyronitrilel (AIBN) under nitrogen. The monomers, Il solvent, and AI~N initiator are added to a round bottom flask, ,I covered with a septum, and degassed by bubbling nitrogen for ;~ 15 minutes. The nitrogen is changed t~ ~ sparge and the flask is warmed to 75C, and a positive nitrogen pressure is maintained in the flask. The monomers are polymerized for 12 hours at 75C. The copolymer product is precipitated into j methanol and isolated by filtration (90% conversion~.
j, The copolymer has a T of about 112C, and exhibits ¦ a ~ of about 180 x 10 esu as measured at 1.34 ~m excitation wavelength. A thin film of the copolymer exhibits a X f about 3 X 10 esu as measured at 1.34 ~m i excitation wavelength.
"
~l - 35 -!i ~l l I.j ~ ~ 3 ~
jl EXAMPLE I v 'This Example illustrates the construction and operation of an optical frequency converting waveguide module utilizing a present invention thin film optical waveguide medium.
A silicon dioxide-coated silicon wafer with a grating ! electrode is constructed by means of the following fabrication ¦! procedures.
A commercially available silicon dioxide-coated silicon wafer is placed in a Varian electron beam vacuum deposition system. A 0.1 ~m layer of 99.999% purity a:Luminum is deposited on the wafer.
AZ-1518 positive photoresis~ (Hoechst) is spin coated on the aluminum-c~ated wafer with a Solitec model 5100 coater~ ¦
A 1.5 ~m photoresist coating is achieved by spinning at 5000 rpm ¦
for 30 seconds. The photoresist coating is dried in a vacuum oven at 90C for 30 minutes.
~ he photoresist coating is patterned by placing the ¦! wafer in contact with a mask of the desired config~ration in a j! Xarl Suss model MJB3 mask aligner, and exposing the masked coating t~ 405 ~m radiation (70 mJ/cm~
The mask is removed, and a thin piece of silicon (1 cm x 2 cm) is placed on the surface of the patterned photoresist as a protective shield, and the combination is exposed to 70 m~/cm~ of 405 ~m radiation. The patterned il - 36 _ 'i ' i ' '2 ~ 3 !
;j , I
'I . I
photoresist is deve1oped ~ith AZ Developer in water (1:1) over a !
period of 60 seconds, and the developing cycle is terminated by washing with deionized water.
i The photoresist-coating of ~he wafer is baked in a jl vacuum oven at 120C for 45 minutes. The ~exposed al~minum pattern is etched with type A et~hant (Transene Corp.) at 50C
~' for 20 seconds, and the etched surface is rinsed with d~eionized ,! water.
j~ The aluminum grating electrode surface of the wafer ,j then is covered with a 1.5 ym cladding layer of 20~ polyvinyl ,~ alcohol (75% hydrolyzed) in water by spin-coating at 5000 rpm j¦ for 30 seconds, and the cladding layer is dried in a vacuum oven Il at 110C ~or two hours.
~, , ~¦ A nonlinear optically active organic layer of 1.65 ~m , thickness is spin-coated on the cladding layer at 3000 rpm. The !
I! spin-coating medium is a 20% solution of an isotropic copolymer ~! ~50/50) of methyl methacrylate/4-(methacryloyloxy-2-hexoxy)-4'-nitrostilbene in trichl~ropropane. The organic layer is dried in a vacuum oven at 160C for one hour.
,i ~n upper cladding layer o~ 1.5 ~m thickness is added by spin-coating a medlum of polysiloxane (GR-651-~, 0wens-Illinois ~ Inc., 25~ solids in l-butanol) a~ 3500 rpm for 30 seconds. The jl cladding layer is dried in a vacuum oven at 110C for 35 minutes. A 0.055 ~m coatlng of aluminum is deposited as an ,l electrode layer on the upper cladding layer~
.1 '.
'l ;
'I
The fabricated waveguide is placed in a Mettler hot , stage, and the unit is raised to 90C at 1C/min. A DC field of 70V~m is applied across the waveguiding organic layer for ten ~? minutes h~ means of the electrodes. The electric field is ~,aintained while the waveguide sample is cooled to r~om temperature at l~C/min. The X nonlinear optical response of the waveguiding medium is 1 ~ 10 esu as measured at 4 ~Im exci tation wavelength.
' The waveguide structure is cleaved at opposite ends to provide two sharp faces to ~ouple light in and out of the , waveguiding organic layer.
Cylindrical lenses are employed to focus and couple i 1. 34 radiation ( O. 01 mJ, 10 nsec wide pulse) into the Il waveguide The waveguide is situated on a rotation ~tage, and ! phase-matched second harmonic generati~n is observed when the l waveguide is rotated until the periodicity satisfies the value ! for phase-matching. Under the described operating conditions, a 0.5-1% amount of the fundamental beam is converted into observed ~! second harmonic radiation.
I A nonlinear optical response occurs in the fabricated ¦j device upon excitation with ~M~ radiation. As the sample is j¦ rotated, the grating ma~ches the required periodicity for !I phase-matching and the second harmonic signal increases, demonstrati~g that phase-matched interaction has occurred I between the fundamental mode TM and its harmonic TM2~ i o o li _ 38 _ i i ~ V tJ
EY.A~PLE V
This Example i~lustrates the construction and operation i of a polarization-insensitive waveguide electrooptic modulator Il utilizing a present invention thin film opti~al waveguide medium.
iA commercially available silicon dioxide-coated silicon wafer is placed in a Varian electron beam vacuum deposition system. A n.l ~m layer of 99.999% purity gold is deposited on the wafer. I
AZ-151~ positive photoresist (Hoechst) is spin-coated on the alu~inum-coated wafer with a Solltec model 5100 coater.
j A 1.5 ~m photoresist coating is achieved by spinning at 5000 rpm for 30 seconds. The photoresist coating is dried ;n a vacuum ! oven at gaoc for 30 minutes.
I The photoresist coating is patterned in the form of ¦ lower electrode by placing the wafer in contact with a mask of i' the desired configuration in a Karl Suss model MJB3 mask i, aligner, and exposing the marked coating to 405 ~m radiation t120 mJ~cm2).
The mask is removed, and the patterned photoresist is developed with AZ-400k Developer in water (1:1) over a period of ~
j 45 seconds, and the developing cycle is terminated by washin~ I
¦I with deionized water~
!i The photoresist-coating of the wafer is baked in a ! vacuum oven at 120C for 30 minutes. The exposed aluminum pattern is etched with type ~ etchant at 50~C for 2a seconds, and the etched surface i~ rinsed with deionized water.
Il . .
,_. . .
i ~
i ~3~3 i; !
! !
The aluminum electrode surface o~ the wafer is covered with a thin llO00 A~ protective polysiloxane layer, fol~owed by a 1.5 ~m lower ~rganic cladding layer of a 20~ solution of an amorphous copolymer (40/60~ of methyl methacrylate/
4-mett1acryloyloxy-2-ethoxy-4'-nitrostilbene in trichl~ropropane by spin-coating at 3000 rpm for 30 seconds, and the cladding layer is dried in a vacuum oven at 160C for one hour~ The organic polymer has a molecular weight of about 30,000, and the cladding layer has a refractive index of 1.42.
The wafer then is exposed tv reactive lon etching for S seconds to improve surface adhesion to ~ubsequent layers. The etching conditions are five standard cubic.centimeters per minute of 2 flowing at lS mtorr pressure, with 30 watts~6 diameter platten of 13.56 MHz r.f. power.
A nonlinear optically active thin film waveguide layer of 1.65 ~m thickness is spin-coated on the lower cladding layer at 3C00 rpm. The spin-coating medium i~ a 20% ~olution of an isotropic copolymer (50/50) of methyl methacrylate/
4-(methacryloyloxy-2-ethoxy)-4'- nitrostilbene in trichloropropane, The organic layer is dried in a vacuum oven at 160C for one hour. The organic polymer has a molecular weight of about 30,000~ and the thin film has a refractive index o~ 1.49 ,, .
I _ 40 _ !
i .i !
il .
A photoresist layer of Az-l5lB is spin-coated on the , thin film waveguide layer at 4000 rpm, and the layer is exposed I to 405 ~m radiativn (120 mJ/cm ). A 0.2 ~m layer of aluminum il is deposited on the photoresist layer. The aluminum layer is '! coated ~ith a photoresist layer, and the layer i~ patterned in ! the form of a Mach-Zehnder interferometric waveguide. The waveguide width is 5 ~m. The Y junction channels separate and , recombine at a full angle of G.3 degrees.
i¦ The upper surface of the waveguide structure is exposed to reactive ion etching for 15 minutes under oxygen plasma conditions as previo~sly described, to remove the m~ltilayers down to the bottom silicon substrate, except for the photoresist coated pattern. The etching cycles ~lso rem3ve the pho~oresist ¦ coating from the aluminum pattern.
The aluminum and lower photoresist layers are removed ! by immersion of the waveguide ~tructure in AZ-400k developer for one minute.
I The substrate and the upper surface multilayer rib j pattern are spin-coated with an upper organic claddin~ layer in the same manner as described above for the lower cladding layer.
Il A 0.1 ~m layar of aluminum is deposited on the upper ! organic cladding layer, and follow~ng the pattern procedures described above an upper electrode is formed on the ~irst channel, ~nd a pair of parallel electrodes are formed on the ~! second channel.
~J3 i i i il . I
The waveg~ide structure is cleaved at opposite ends to provide two sharp faces to couple light in and out of the j waveguiding thin film and cladding assembly.
!, Molecular orientation of the two polymeric waveguide ¦1 assembly sections between the two sets o electrodes respectively is accomplished by application of applied electric fields ~y the sets of electrodes.
il The fabricated waveguide device is placed in a Mettler Il hot stage, and the unit is raised to 90C at 1C/min. A ~C
i! field of 70 V~m and an AC voltage of 5 volts sine (10,000 t) is ~; i applied to one set o~ eleotrodes, and a variable DC voltage and ~¦ an AC voltage of 5 volts sine (lO,ODO t) are applied to the other set of electrodes.
¦ Ob~ective lenses ~lOXI are employed to focus and couple ¦1 1.34 radiation ~m (100 mW continuous wave) into the Mach-zehnder Ij waveguide. The output of the waveguide is passed through a lOX
!! microscope objective, a polarization beam splitter, and then ,¦ into two opt;cal detectors. The detector signals are transmitted to two lock-in amplifiers.
Both amplifiers are tuned for a signal at iO,OOO Herz, and the variable DC ~oltage to the first set of electrodes is il adjusted until the signals in the two amplifiers are identical.
l The waveguide unit is held at 90C for 20 minutes under I the adjusted applied fields, and the applied fields are ¦~ maintained while the waveguide unit is cooled to room temperature at 1Ctminute.
i !
! .
~3~&33 1 During operation of the waveguide, the effected light ~! modulation is polarization-insensitive because the voltages '¦ applied to the two sets of electrodes are balanced to achieve '¦ equal phase ~odulation of the TE and TM modes of transmitted Il light.
ii , .
i I
Il :
Claims (30)
1. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter.
2. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is a copolymer with at least one comonomer having pendant side chains which exhibit second order nonlinear optical susceptibility .beta..
3. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where P' is a polymer main chain unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms;
M' is an organic structure which exhibits second order nonlinear optical susceptibility .beta.; and the polymer has a weight average molecular weight in the range between about 5000- 200,000.
where P' is a polymer main chain unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms;
M' is an organic structure which exhibits second order nonlinear optical susceptibility .beta.; and the polymer has a weight average molecular weight in the range between about 5000- 200,000.
4. A thin film optical waveguide medium in accordance with claim 3 wherein the polymer main chain is a polyvinyl structure.
5. A thin film optical waveguide medium in accordance with claim 3 wherein the polymer main chain is a condensation polymeric structure.
6. A thin film optical waveguide medium in accordance with claim 3 wherein the polymer main chain is a polysiloxane structure.
7. A thin film optical waveguide medium in accordance with claim 3 wherein the polymer is characterized by an external field-induced alignment of pendant side chains.
8. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where PV is a main chain polyvinyl unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms; X is an electron-donating group; Y is or and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about 40°-250°C.
where PV is a main chain polyvinyl unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms; X is an electron-donating group; Y is or and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about 40°-250°C.
9. A thin film optical waveguide medium in accordance with claim 8 wherein the polyvinyl polymer contains a recurring acrylate monomeric unit.
10. A thin film optical waveguide medium in accordance with claim 8 wherein the polyvinyl polymer contains a recurring vinyl halide monomeric unit.
11. A thin film optical waveguide medium in accordance with claim 8 wherein the polyvinyl polymer contains a recurring vinyl carboxylate monomeric unit.
12. A thin film optical waveguide medium in accordance with claim 8 wherein the polyvinyl polymer contains a recurring alkene monomeric unit.
13. A thin film optical waveguide medium in accordance with claim 8 wherein the polyvinyl polymer contains a recurring arylvinyl monomeric unit.
14. A thin film optical waveguide medium in accordance with claim 8 wherein the polymer is characterized by an external field-induced alignment of pendant side chains,
15. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where CP is a main chain condensation polymer unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms X is an electron-donating group; Y is or and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about 40°-250°C.
where CP is a main chain condensation polymer unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms X is an electron-donating group; Y is or and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about 40°-250°C.
16. A thin film optical waveguide medium in accordance with claim 15 wherein the main chain condensation polymer is a polyester structure.
17. A thin film optical waveguide medium in accordance with claim 15 wherein the main chain condensation polymer is a polyamide structure.
18. A thin film optical waveguide medium in accordance with claim 15 wherein the polymer is characterized by an external field-induced alignment of pendant side chains.
19. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 1?8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where PS is a main chain polysiloxane unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms; X is an electron-donating group, Y is or and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about 40°-250°C.
where PS is a main chain polysiloxane unit; S' is a pendant spacer group having a linear chain length of between about 2-12 atoms; X is an electron-donating group, Y is or and Z is an electron withdrawing group; and the polymer has a glass transition temperature in the range between about 40°-250°C.
20. A thin film optical waveguide medium in accordance with claim 19 wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where R is a C1-C10 hydrocarbyl substituent; and S', X, Y
and Z are as previously defined.
where R is a C1-C10 hydrocarbyl substituent; and S', X, Y
and Z are as previously defined.
21. A thin film optical waveguide medium in accordance with claim 19 wherein the polymer is characterized by an external field-induced alignment of pendant side chains.
22. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 1.34 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where m and m1 are integers which total at least 10; R is hydrogen or a C1-C4 alkyl; n is an integer having a value of 2-8; X is oxygen, sulfur or an amino or cycloamino group;
R2 is a C1-C12 alkyl or cycloalkyl group; Y is or and Z is an electron-withdrawing group; and the polymer has a glass transition in the range between about 50°-200°C.
where m and m1 are integers which total at least 10; R is hydrogen or a C1-C4 alkyl; n is an integer having a value of 2-8; X is oxygen, sulfur or an amino or cycloamino group;
R2 is a C1-C12 alkyl or cycloalkyl group; Y is or and Z is an electron-withdrawing group; and the polymer has a glass transition in the range between about 50°-200°C.
23. A thin film optical waveguide medium in accordance with claim 22 wherein the X substituent in the formula has the structure .
24. A thin film optical waveguide medium comprising an amorphous polymer which exhibits a second order nonlinear optical susceptibility X(2) of at least about 1 x 10-8 esu as measured at 134 µm excitation wavelength, and exhibits a light transmission optical loss of less than about one decibel per centimeter; wherein the polymer is characterized by recurring monomeric units corresponding to the formula:
where m and m1 are integers which total at least 10; R is hydrogen or C1-C4 alkyl; L is -NR1 - or ; R is hydrogen or a C1-C4 alkyl group; Q is nitrogen or a -CH-radical; R2 is a C1-C12 alkyl or cycloalkyl group; the m monomer comprises between ahout 30-70 mole percent of the total monomers; and the polymer has a glass transition temperature in the range between about 50°-200°C.
where m and m1 are integers which total at least 10; R is hydrogen or C1-C4 alkyl; L is -NR1 - or ; R is hydrogen or a C1-C4 alkyl group; Q is nitrogen or a -CH-radical; R2 is a C1-C12 alkyl or cycloalkyl group; the m monomer comprises between ahout 30-70 mole percent of the total monomers; and the polymer has a glass transition temperature in the range between about 50°-200°C.
25. A thin film optical waveguide medium in accordance with claim 24 wherein the polymer additionally contains recurring units of a third monomer.
26. A thin film optlcal waveguide medium in accordance with claim 24 wherein the polymer has an external field-induced alignment of pendant side chains.
27. A thin film optical waveguide medium in accordance with claim 24 wherein the waveguide medium has a two-dimensional channel structure for single mode wave transmission.
28. A thin film optical waveguide medium in accordance with claim 24 wherein the waveguide medium has a spatial periodic structure of aligned polymer side chains for phase matching of propagating wave energy.
29. A thin film optical waveguide medium in accordance with claim 24 wherein the waveguide medium has a spatial periodic structure of aligned polymer side chains for phase matching of propagating wave energy, and the spatial periodicity of aligned polymer side chains is bidirectional in structure.
30. A thin film optical waveguide medium in accordance with claim 24 wherein the thin film is in a laminated assembly with an upper organic cladding layer and a lower organic cladding layer, each of which has a lower index of refraction than the thin film waveguide components and which exhibits second order nonlinear optical susceptibility X(2).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/468,676 US5002361A (en) | 1986-10-03 | 1990-01-23 | Polymeric thin film waveguide media |
| US468,676 | 1990-01-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2033463A1 true CA2033463A1 (en) | 1991-07-24 |
Family
ID=23860778
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2033463 Abandoned CA2033463A1 (en) | 1990-01-23 | 1990-12-31 | Polymeric thin film waveguide media |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2033463A1 (en) |
-
1990
- 1990-12-31 CA CA 2033463 patent/CA2033463A1/en not_active Abandoned
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