CN1377470A - Deep UV laser internally induced densification in silica glasses - Google Patents

Abstract

A method of writing a light guiding structure in a bulk glass substrate including selecting a bulk glass substrate made from a soft silica-based material; and focusing an excimer laser beam at a focus within said substrate while translating the focus relative to the substrate along a scan path at a scan speed effective to induce an increase in the refractive index of the material along the scan path relative to that of the unexposed material while incurring substantially no laser induced breakdown of the material along the scan path. Various optical devices, including waveguides can be made in this way.

Description

Extreme ultraviolet laser increases the quartz glass internal density

The U.S. Provisional Patent Application 60/156,737 that the right of priority that the present invention requires was submitted to from September 30th, 1999, this provisional application also here together as a reference.

Background of invention

The present invention relates to extreme ultraviolet light (＜300nm) in the method that forms optical device effectively on glass, particularly relevantly change and in glass ingredient, form the method for writing direct of optical waveguide structure by the photoconduction induced refractive index.The present invention also relates to make optical device with the method for writing direct.The invention still further relates to the structural glass substrate, the waveguide that density increases can be directly and is write effectively in this substrate.

At communication field, the optical device such as optical waveguide and Bragg diffraction grid is well-known.In optical waveguide, also can be by the high index light conducting that centers on than the low-refraction covering with a large amount of optical informations of the long distance of little signal attenuation ground transmission.Optical waveguide fibre is the prototype of this class device.This fibrid of making by means of the different clad material of different core material that high index of refraction is arranged and low-refraction has provided the waveguiding structure of determining.The Bradley grid is the optical device of another kind of type, and it can and can tell narrow wavestrip as wave filter from the signal of broad.Prevailing commercial material is the silica based component material that mixes in the communication applications of photocon, as Ge-doped silicon dioxide fibre core and pure, the anhydride silica of no hydroxyl.

As everybody knows, laser can be used for changing the refractive index of glass, also can produce volume defect in glass.About the former, the laser of known use pulse UV radiation can write the Bradley grid in Ge-doped silica core fiber.Recently, " writing direct " laser means of formation optical waveguide has been disclosed in the vitreum transparent to the femtosecond laser wavelength.In this method, pulse focuses on a slice perpendicular on the focus in the silicon dioxide of incident beam direction translation from start to finish more than or equal to the 810nm laser of 120fs.Under a specific condition, refractive index increases about 10 ^-2The order of magnitude, this condition is a focus whole exposure region scanning ten times.

Potential problems that use the short pulse laser focusing to form the method for writing direct of waveguide in structural glass are over-exposed.Too high-octane radiation energy causes the volume defect in the glass.The volume defect of glass and damage can make the undesirable decay of light signal generating by the glass transmission.

Another problem that the method for writing direct is made optical texture is the balance between the dimensional stability of relevant write device, promptly about cause needed laser of desirable variations in refractive index and energy in baseplate material.

In order to make the laser method industrialization of writing direct, the material change of refractive must be in that reasonably the write time be interior realization.This method of writing direct that just requires to produce the silica based optical device of enough increase refractive indexes will be carried out with acceptable high writing rate.Such method can be used for writing in a continuous bulk suitable material and connect any leaded light waveguide at 2, perhaps makes other optical device, as the Bradley grid.

Germanium-doped silica is commonly used can be with the material of light change as refractive index.In the photosensitive response of germanium-doped silica, add H ₂It is the method that typically improves the glass photosensitive response.In this case, the mechanism of refractive index raising is by the mechanism that forms colour center by the Kramer-Kronig relation.Add H ₂Use cause the result of logic, comprise block of material is added H ₂The needed time, particularly hanging down to making H ₂Inject H under the temperature that is not enough to react with material ₂The time prevention property ground that becomes long.For example, the quartz glass plate that 3mm is thick adds H under 150 ℃ ₂Need 36 days.In case make H ₂Enter material, the result just becomes and contains H ₂Glass sheet, although concerning block of material, this is the result who has very much.

Provide and do not needed by making density improve refractive index with adding H ₂Handle the advantage of material.Concerning such as optical fiber and this class small size glass structure of thin slice, add H ₂Be operable, so under this size, H ₂Can easily spread into, for carrying out three-dimensional addressing and write in the vitreum of large-size, just can not implement, this is because H ₂Be diffused into the absorption characteristic aspect existing problems and the difficulty of vitreum deep inside and glass.The advantage that another of this invention dived is with adding H ₂Mix germanite English and typically experienced the thermal annealing under the low temperature, grid are " fixing " in the meantime, thereby have write the feature of thermal stability.This thermal annealing has reduced the efficient of about 30% grid and assisted in ensuring that minimizing of further changing aspect efficient.The mechanism that creatively utilize to increase density obtained for " fix " even and do not need heat treated characteristics and under several Baidu temperature, still keep better hot toughness usually, thereby it is interior from its surperficial degree of depth above 2cm to be written to fast shape glass dearly.

As everybody knows, high-purity fused quartz for example, can produce measurable density with excimer laser tablet system (laser beam makes this mean pole exposure) in lasting exposure under high-energy radiation and the laser and increase effect in the fused quartz optical element.

Brief summary of the invention

An object of the present invention is to provide a kind of improved method of writing direct that in silica based material substrate, forms guide structure, particularly wish in glass, to write inherently and effectively the three-dimensional light guide structure.The extreme ultraviolet laser beam that focuses on is passed inner the moving with the glass inside in whole high-density glass waveguide core structure of large scale bulk glass and is formed high density waveguide core structure, and this structure can be passed block glass at a plurality of planes and a plurality of outside surface of three block glass of directions process three-dimensionally.

Method of the present invention is included in writes direct in the structural glass forming waveguide core, the degree of depth of this structural glass from the surface to the body in 1cm at least, 2cm at least preferably, 3cm and preferably 4cm at least at least better.The present invention includes the optical waveguide of making in the three-dimensional block glass of the high density waveguide core of writing direct and have inner non-surperficial core diameter part, best 2cm at least, preferably 3cm and preferably 4cm at least at least from block glass outer surface 1cm at least.

Further purpose of the present invention provides the method for writing light entrance structures thereof in the silica based material.

According to an aspect of the present invention, find that soft silica based material increases the laser display sensitivity of writing light entrance structures thereof in vivo.

According to another aspect of the present invention, provide and use in glass, write direct guide structure and of laser to the substance damage of glass.

According to also aspect of the present invention, be provided at the method that writes the three-dimensional light structure in the quartz substrate glass, particularly the invention provides laser spot and move the method that improves refractive index through quartz base plate at X, Y and Z direction.

According to a further aspect of the invention, various optical device and combine have been disclosed with the optical texture of method manufacturing as described herein.Present invention resides in usefulness＜300nm extreme ultraviolet laser beam foucing in bulk soft (annealing point＜1350 ° K) quartz glass and optionally produce interior zone that density increases to form high density waveguide core path.

These and other aspect of the present invention can become very clear by the explanation here concerning the professional and technical personnel.

The accompanying drawing summary

Fig. 1 (A) and Fig. 1 (B) represent that respectively the top writes and the incoming laser beam that axially writes the direction of scanning.

Fig. 2 (A) and Fig. 2 (B) represent scanning beam figure and the waveguide cross sectional shape that the top writes and axially writes respectively.

Fig. 3 (A) and Fig. 3 (B) are illustrated in the skeleton view that the top of the three-dimensional optical device that writes direct in the blout writes.

Fig. 4 represent density increase with in the funtcional relationship of laser emission to the exposure of glass exposure.

Fig. 5 represents for the glass that uses among the present invention, the relation of vacuum outer transmission of dress and wavelength.

Fig. 6 represents quartz glass, the Δ P/P that 193nm excimer laser according to the present invention causes and the relation of dosage.

Fig. 6 A is the partial enlarged drawing of Fig. 6.

Fig. 7 is the relation that increases between the softening temperature (inverse of annealing temperature) of density (natural logarithm of prefactor a) and quartz.

Fig. 8 is the figure less than the 300nm laser explosure.

The optical device that Fig. 9 (A)～(E) expression is constructed in accordance.

The detailed description of invention

The method of writing direct that forms guide structure according to the present invention in soft silica glass blocks substrate may further comprise the steps: the substrate of selecting to write guide structure from the silica based material; To focus on smaller or equal to the UV laser beam of 300nm on the focus of substrate inside so that focal position increases at density of material; Substrate and focus move each other to form scanning pattern and to increase along this density in the substrate of scanning pattern of glass and form guide structure.Wavelength X optionally forms the scanning pattern that density increases less than the laser beam of 300nm in block glass, thereby it has high refractive index and still has lower original region of low refractive index to be wrapped up for the density on glass of focusing does not increase.Glass density increases by two-photon absorption and produces and square relevant with the laser focusing beam intensity.

The focusing of laser beam and non-focusing optical beam ratio have strengthened the peak strength of light beam greatly.Thereby high-intensity focused beam make glass density increase along with beam focus along moving on the quartz glass samples, cause the increase of refractive index on the glass path that the density that causes along beam focus increases.The high index of refraction path district of the glass that final densities increases can leaded light, thereby can not increase the function that realizes optical waveguide in the path of adjacent glass parcel of density around.

Shown in Fig. 1 (A), " top increases the density wiring method " is that sample moves on 13 direction, and direction 13 is vertical substantially with the incident beam that increases density." axially wiring method ", to be sample moved in 13 direction, and direction 13 is substantially parallel with incident beam, shown in Fig. 1 (B).Skilled professional is easy to judge, the top writes also and can realize by moving simultaneously in directions X, Y direction or X and Y direction.

When the top writes focus and moves in the direction of scanning by sample, can form oval-shaped waveguide usually and be cut into.When axially writing focus and move in the direction of scanning, form the circular waveguide cross section usually by sample.For the waveguide that forms has round section, better with axially writing the waveguide meeting usually.In order to write the continuous linear waveguide longer continuously, can use the top to write than condenser lens.

With reference to Fig. 3 (A) and 3 (B), further describe the ability that in sample, writes three-dimensional waveguide with the existing direction of writing direct.Laser beam 2 scioptics 5 focus on the focus that is arranged in glass sample 4.Sample in X, Y and Z direction from a certain position X ₁, Y ₁, Z ₁, depth D ₁Mobile second place X ₂, Y ₂, Z ₂, depth D ₂Cause that glass increases along the refractive index of scanning pattern 9, thereby form the optical waveguide passage of three-dimensional extension between first and second positions in sample.If require the plane, i.e. two-dimensional waveguide, then X ₁Can look like X ₂The same, Y ₁Can look like Y ₂The same or Z ₁Can look like Z ₁The same.Linear waveguide, then X if desired ₁, Y ₁Can be respectively as X ₂, Y ₂The same, Y ₁, Z ₁Can be respectively as Y ₂, Z ₂The same or X ₁, Z ₁Can be respectively as X ₂, Z ₂The same.

Laser instrument can be to produce any laser instrument of the wavelength of proper strength less than the 300nm UV laser beam.The example of available laser instrument is middle for example below to be described.Wavelength is levied with several bundle parameter marks less than the UV laser beam of 300nm.In preferred embodiment, use excimer laser.The pulse width of laser is more preferably greater than 5nsec.Excimer laser is the light-pulse generator of pulse width between 15～60nsce.The non-focusing energy of each pulse of excimer laser is at 2～100mJ/cm ²Scope increases this pulse energy density by focussed laser beam.Preferably use the excimer laser of wavelength, for example KrF or ArF excimer laser less than 300nm.Except that excimer laser, can also be with non-excimer laser as the lasing light emitter that increases density, its wavelength is lower than 300nm and suitable intensity is arranged.Replace the light source of excimer laser to comprise picture Nd YAG and YLF, the solid state laser of Ti process for sapphire-based one class.Wavelength is less than the Ultra-Violet Laser beam intensity of 300nm and distribute preferably by focusing on (preferably using lens) focus in the glass of increase density, when beam diameter is 10 microns, and focus strength 〉=10mJ/cm ²Intensity in increasing the glass of density on the focus preferably 〉=50mJ/cm ², best 〉=100mJ/cm ²Concerning increasing the soft silica glass of density in inside, the wavelength that uses has the laser beam that the focuses on output that increases density flow less than the suitable ultraviolet laser of 300nm on the focal spot of glass inner focusing into about 10 microns (10 ± 5 microns) that increases density, strength range is from 10mJ～150mJ/cm ²This wavelength is used for producing an increase density write area less than the focus of the increase density of 300nm in block glass, be lower than under the 300nm wavelength should bulk glass the inner transparent degree greater than 70%/cm, better be greater than 90%/cm, be more preferably, preferably greater than 98%/cm greater than 95%cm.When Ge-doped quartzy during as the soft silica body glass substrate that writes at the focus place, the wavelength of extreme ultraviolet laser beam is preferably in 220～250nm scope more than 220nm.When using no germanite English as the soft silica bulk glass substrate that writes at the focus place (undope high-purity fused quartz or with the soft adulterant of non-germanium), the wavelength of extreme ultraviolet laser beam is preferably in 180～220nm scope more than 180nm.Intensity on the focus of increase density glass is enough to make the glass density increase but is not enough to form the space on the focus of exposure glass.This increase density focus of lacking than the high strength micro-tunnels has been avoided the physical damnification of glass and has been avoided laser to cause the glass damage, as forming the space.

In the example that the glass focus of the relatively-stationary increase density of glass sample below moves, the laser spot that experienced technician understands easily the glass of the increase density that substitutes moves with respect to fixed sample or increases the laser spot of density and sample and can relatively-stationary reference point moves simultaneously to reach sample and to form desirable speed of related movement between the pattern of focus.With respect to unexposed material, with cause along scanning pattern make sweep velocity that density of material increases with respect to substrate along the scanning pattern moving focal point, and do not cause material damage at scanning pattern basically simultaneously, can use the scope of sweep velocity to be about 1 micron to 1 millimeter of per second.

Accompanying drawing has been described and has been suitable for being used in the glass substrate that writes the quartz material sample of the present invention, has basically and hands over rectangular plane surface each other, and experienced technician recognizes that the present invention is not limited to the board structure of this rule.Even the present invention can be used for the optical waveguide of writing direct on substantially any rule or the irregular three-D sample.But perpendicular to sample surfaces, incident beam is by this sample with respect to the feasible light beam basically of incoming laser beam in position that had better sample.Compare with thin layer, substrate is 3D shape preferably.Compare with thin layer, substrate is 3D shape preferably.The thickness of substrate is several times of path thickness preferably, and preferably at least 100 times, 500 times better, preferably at least 1000 times.

The composition that can write the substrate of optical waveguide structure with the present invention therein is the silica based material, comprises the quartz system that plain fused quartz and codope, three are mixed.Optical property and requirement according to various hope are extensive use of at communication device, thereby recommend to use the silica based material.The usually recommended usefulness of the quartzy system of binary and ternary in the present invention.Binary and ternary silica based material are because they have strengthened the sensitivity that increases density and recommended use.

Use " silica based material " to mean that glass ingredient comprises quartz, and do not have alkaline metal basically, earth alkali metal and other transition metal and can cause other impurity that 1300～1600nm scope absorbs.In the silica based material that the present invention uses, do not find to be higher than this class impurity of 10ppb (per 10/1000000000ths).

In general the present inventor has been found that the substrate with the bulk substrate ratio of soft silica based structures manufacturing is made with admant English sill under the situation of not sacrificing the variations in refractive index size, can more easily write waveguide.Use the excimer laser optical waveguide structure that in the soft silica based structures, writes direct to show sensitiveer than in admant English based structures glass, writing.

In order to disclose this point, " soft " quartz substrate material is defined as and mixes or the silica based material that undopes, and it is 5mol%GeO that its annealing temperature is lower than component ²-95mol%SiO ²The Ge-doped glass of component, promptly the annealing temperature of silica based material is lower than 1380 ° of K preferably.Silica-based glass is binary or the ternary silica based material of 1380 ° of K being lower than of annealing temperature preferably, and better annealing temperature is lower than 1350 ° of K, is preferably between the 900-1325 ° of K.Annealing temperature is defined as that viscosity of material is 10 under this temperature ^13.6Pool.

Plain quartz substrate material package is drawn together, and as the bussiness class fused quartz, as high-purity fused quartz 7980 glass of the HPFS trade mark of Corning Incorporated, its annealing temperature is between 1261 ° of K-1323 ° of K.Soft high-purity fused silica glass used in this invention is moisture high-purity fused quartz, and the DH content of its unit weight is preferably greater than 100ppm, better 200ppm, preferably greater than 500ppm greater than 50ppm.For doped system, can be used in the soft silica preferably that adulterant is the oxide of element boron, phosphorus, aluminium and germanium, as monox (B ₂O ₃), aluminium oxide (Al ₂O ₃), phosphorous oxide (P ₂O ₅) and germanium oxide (GeO ₂).Can use the impurity concentration of wishing arbitrarily.

In binary boron doping silica based system, the content of monox can arrive 20wt% or higher.The scope of binary glass system components is from 9wt%B ₂O ₃-91wt%SiO ₂To 20wt%B ₂O ₃-80wt%SiO ₂Component is 9wt%B ₂O ₃-91wt%SiO ₂Annealing temperature be about 1073 ° of K.Component is 20wt%B ₂O ₃-80wt%SiO ₂Annealing temperature be about 999 ° of K.

In binary phosphorus doping silica based system, the content of phosphorous oxide also can reach 20wt% or higher, and scope is 7-20wt% preferably.The compositional range of binary glass system is from 10wt%P preferably ₂O ₅-90wt%SiO ₂To 7wt%P ₂O ₅-93wt%SiO ₂7wt%P ₂O ₅-93wt%SiO ₂The annealing temperature of component is about 1231 ° of K.

In binary aluminium doping silica based system, alumina content can be gone up 20wt% or higher, and best scope is 10-20wt%.For example can use 10wt%Al ₂O ₃-90wt%SiO ₂The binary glass system.

In the Ge-doped silica based of binary system, the content of germanium oxide can arrive 22wt% or higher, best scope about 15wt% between the 25wt%.The best composition scope of binary glass system is from 20wt%GeO ₂-80wt%SiO ₂To 22wt%GeO ₂-78wt%SiO ₂20wt%GeO ₂-80wt%SiO ₂The about 1323 ° of K of annealing temperature, and 22wt%GeO ₂-78wt%SiO ₂Annealing temperature be about 1311 ° of K.Alternative scope is the germanium oxide from 14%-9%.The content of the germanium oxide of binary composition from 9% to 22%.

But in the present invention, in the time that Ge-doped glass can be used, do not need to use germanium oxide.Therefore, the present invention can be used in the quartz glass of no germanium.In preferred embodiment, soft silica glass is no Ge's basically.

" firmly " quartz substrate material is defined as annealing temperature, and to be higher than component be 5mol%GeO ₂-95mol%SiO ₂The doping of glass system annealing temperature or the silica based material that undopes, just annealing temperature is higher than the material of 1380 ° of K.The example of admant English sill comprises the anhydrous fused quartz of the about 1425 ° of K of annealing temperature.Knowing per capita of this specialty, anhydrous fused quartz do not have residual hydroxyl family in fact, and have higher level as healthy and free from worry HPFS  bussiness class fused quartz, for example greater than 200ppm/wt with greater than the hydroxyl groups of 800ppm.

The silica based material that uses among the present invention can prepare with flame hydrolysis technology.In this technology, the silicon that contains the gas molecule reacts in flame and forms SiO ₂Particle.The hot surface of the rotary body of these particle deposition in being attached to the liquid of viscous is cooled to glassy state (solid-state) then very much.Such manufacturing process is called vapor phase hydrolysis/oxidation skill or abbreviates flame hydrolysis technology as.But, also can use other already known processes.The silica based material is preferably with the direct deposit of step and the technology manufacturing of condensing.

The applicant has been found that quartz glass exposure under excimer laser radiation can cause variable density, and being called the density that makes in the glass increases.Under laser treatment, glass density is big more, and it is high more to be accompanied by refractive index.By, for example exposure can cause variable density under 248nm and the 193nm quasi-molecule laser pulse.When the non-focusing pulse energy is 10-100mJ/cm at least ²The time, pulse width can be 5-30nsce, better is 20-30nsce.In glass, write figure and form waveguide channels by be used for making density to increase in glass substrate inner focusing laser beam.

The useful especially quartz glass that is exposed is the glass of maintenance highly transparent as discussed above, especially under extreme ultraviolet light.This is because for quasi-molecule exposure, sample to the excimer laser wavelength at least 70%-90%/cm be transparent basically.Therefore, can cause that density increases in the depths in glass.The mechanism that increases density preferably is to reduce and the biphotonic process of the two-photon absorption rate that increases with wavelength, and soft silica glass is to the transparent glass of the shortest wavelength preferably.

Have, have been found that glass is soft more, as the measurement by low Tg or other viscosity～temperature relation, such as the measurement of annealing or softening humidity, the variation that causes that the glass refractive index is proved is just sensitive more.

The blout glass substrate sample of polishing is exposed under the excimer laser radiation by an aperture, its experimental provision is at D.C.Allan, C.Smith, N.F.Borrelli and T.P.Weward III.OptLett.21924), 1960 (1996) and N.F.Borrelli, C.Smith, D.C., Allan and T.P.SewardIII.J.Opt.Soc.Am., B.14,1606, described in (1997), incorporated by reference here.

The laser instrument that is used for 193nm and 248nm exposure is Lumonics 600.With the energy of Molectron thermal detector monitoring by the aperture.The caused optical phase of exposing uses ZYGO Mark-IV instrument to carry out the measurement of interferometer type.For measuring light degree phase shift, " unrestricted " density increase Δ p/p obtains by the help of finite element model.Use unrestricted density to increase geometry and spatial form that the tolerance that increases as density has been considered exposing light beam.The application of the character of model and it is all people such as Allan, SPIE Vol.3578, and 16, illustrated in (1998), quote for referencial use at this.In brief, when exposure region shrank under density increases, finite element model was used for illustrating the elastic response of glass, and allowed exposure and non-exposed area photoelasticity response integration.

Glass in the Table I exposes under the 193nm excimer laser and causes density to increase.In Table I, be illustrated in recurrence interval 30ns, 106 pulses, 10mJ/cm ²The unrestricted density of exposing under the pulse energy increases.The numerical value of caused refractive index is that the density increase multiply by 0.4 roughly.

Table 1

The comparison of the unrestricted deflation of 193nm excimer laser exposure

0.3MW/cm ², 106 pulses

ΔP/P(10 ^-6)

SiO 2(the HPFS  of Corning Incorporated fused quartz 7980	?1.6
		78％SiO 2-22％G 4O 2	?14
?80％SiO 2-20％B 2O 3	?388

The actual relationship that density increases as the function of exposure is shown in Fig. 4 to three samples.Among Fig. 4, X-axis is a dosage, and Y-axis is that density increases.Cause variations in refractive index to hint the key parameter of the softness of glass consumingly to excimer laser as getable refractive index variable quantity from the variation that the quartzy a series of refractive indexes to quartzy germanium monoxide to quartz-boron that undope increase.The germanite glass ratio undopes quartzy soft, and boron glass is much softer than germanite glass.

Under any temperature, the difference of viscosity can be estimated by following formula between quartz and the germanite English,

Logζ _Si-Ge-Logζ _Si＝-0.5Δ

ζ is a viscosity in the formula, and Δ is the Δ n/n that represents with percentage.GeO to 20% ₂, Δ is 10%, so germanite English glass thinks softer than quartz.For boron, this effect even more remarkable.Component is 10molB ₂O ₃/ SiO ₂Its softening temperature of glass than quartzy low about 300 degree.Other more the binary system of soft glass comprise the oxide of phosphorus and aluminium.For example, at P ₂O ₅P for 10mol% ₂O ₅/ SiO ₂The lower softening temperature that low 500 degree are arranged.

In order to cause that less than the extreme ultraviolet laser of 300nm density increases and maximum variations in refractive index with wavelength, glass preferably comprises softer component, such as boron.The size that changes is proportional to the influence of doping component on the softening temperature.The present invention preferably includes with the softening quartz glass of softening adulterant.

By suitable selection exposure wavelength, glass and wave guide process method, can cause that the contribution of the density increase of variations in refractive index maximizes and provide heat-staple waveguiding structure.

Have been found that the speed that quartz glass density increases is faster when replacing the excimer laser of 248nm with 193nm, perhaps fast 5-10 doubly.For example, with 190nm wavelength, 330mJ/cm ²Intensity, frequency 100Hz pulse only need 16 minutes refractive indexes just can change 10 ^-4

To quartzy and mix GeO ₂, B ₂O ₃And P ₂O ₅The quartzy system of binary carried out the direct measurement that density increases speed.Measuring method comprises that the coherence that optical phase moves measures, and this phase shift is to produce by the exposure of controlling respectively 248nm and 193nm excimer laser radiation.Listed the measurement result of on the block glass substrate sample of various components, being done in the table 2.Form the block of pre-sizing by the flame deposit of cigarette ash, then, this block is agglomerated to block glass and forms sample.The crucial part of this mensuration is to use finite element model, and this model allows to parse significant in essence " unrestricted " density and increases a Δ P/P.The physical process that the density that wavelength causes less than the Ultra-Violet Laser of 300nm increases is summed up in this.Glass density increases the variations in refractive index that concerns that produces in the glass of finite element model for the bulk density increase provides method.

Have been found that with following power rule form and can represent easily to increase behavior as the unrestricted density of the function of laser explosure. $\frac{\mathrm{\Δ\ρ}}{\mathrm{\ρ}}=a{\left[\frac{F^{2}N}{\mathrm{\τ}}\right]}^h$

Item in the bracket, the product of the quadratic sum umber of pulse of peak value stream increased from observed density divided by the effective impulse cycle to be had correlativity with this product and releases.See people SPIE3518 such as Allan, 16 (1998), complete here citation is with for referencial use.This form of the data fit of each sample the results are shown in the following table 2.This complete characteristic that meets is influenced by specific selection to a great extent.From data, very clear, as the function of component, density increases very different.Yet by measuring, for example annealing temperature has also been found strong related with relative " softness " of glass.

In the quartzy situation of mixing, the density that the 248nm radiation produces increases the density that produces than 193nm radiation and increases little ten times.At GeO ₂In the sample, little 40 times.Therefore, density increases except outside the Pass having with component, also depends on optical maser wavelength consumingly.

For this experiment, 30ns, 150mJ/cm have been used ², 10 ⁵The exposure of pulse.Final variation at the glass refraction of 193nm radiant exposure provides in table 2.

Table 2

The density that 193nm laser produces increases the comparison as the component function

The sample label	Component % weight	The factor	Annealing point K	??Δn(10 -4)
					????A	?????SiO 2(anhydrous)	????0.27	????1423	????-
????B	?????7P 2O 5-93SiO 2	????2.33	????1231	????0.02
					????C	?????20GeO 2-80SiO 2	????45	????1323	????1.4
????D	?????9B 2O 3-91SiO 2	????23	????1073	????0.7
					????E	?????20B 2O 3-80SiO 2	????157	????999	????4.7

This provides in the quartzy system of binary metal oxide, and wavelength is the strong correlation function of component less than the speed that the Ultra-Violet Laser of 300nm causes density to increase.The speed that the density that excimer pulsed laser produces increases increases with the metal oxide composition.The glassy phase of representing with annealing temperature increases good relevance between the speed to " softness " and density.To all glass, find that also density increases the majorant relation between speed and the excimer laser wavelength, the density increase speed of 193nm wavelength is greater than the 248nm wavelength.

Following glass obtains with flame hydrolysis.Healthy and free from worry HPFS  quartz is the SiO of directly deposit and simultaneously and a direct cigarette ash deposit of step from flame/condense ₂Condense in together, in Fig. 4 to Fig. 6, the high-purity fused quartz standard laid down by the ministries or commissions of the Central Government of HPFS  is annotated HPFS.Other glass is then to be agglomerated in the block glass then by the cigarette ash deposit.In this technology, the cigarette ash blank of porous is to be formed by previous metal flame hydrolysis.Condense in together under the dry then atmosphere of this porous cigarette ash blank.Form non-doped fused silica by this two step process and lower remaining OH concentration is arranged than HPFS  quartz.Lower OH concentration had both influenced the optical clarity that is lower than the 170nm wavelength light, also influenced the annealing temperature of non-doped fused silica.

Binary glass is also with the preparation of two step process, and to form doped porous cigarette ash blank, porous cigarette ash blank condenses multiple metal (B, P, Ge) precursor then with quartzy precursor hydrolysis.The vacuum ultraviolet transmitted spectrum of various silica-based glass is illustrated in Fig. 5.

The unrestricted density of the glass of 193nm exposure increases and dosage

Relation be shown in Fig. 6.F is with mJ/cm ²Each pulse energy density of expression, N are that τ is the square type laser pulse width of representing with nsec with the umber of pulse of 1,000,000 expressions.The definition of this dosage is able to from the correlativity of observing the density increase.

The power rule that the density increase that 193nm laser is produced is fit to use is illustrated in Fig. 6.The numerical value of prefactor a is listed in table 3.Except that Ge-doped glass, the speed that density increases is relevant with the softness of glass.Promptly under the fixed temperature, the viscosity of glass is low more, and the speed that produces the density increase less than the 300nm wavelength laser is just fast more, and temperature is corresponding to the annealing point that is used for characterizing physical property, and the annealing temperature that measures can find in table 3.The relation that laser produces between density increase and glass " softness " is shown in Fig. 7, the relation of having drawn 1n (a)～annealing temperature inverse.Density increases the value representation with prefactor a in the equation, and b is fixed as 0.53 in the equation.Meet straight line and proposed the activation that density increases, the potential barrier of structural rearrangement is 1.7eV there.Bear tight structure more structural rearrangement concern that mechanism is still unclear, but this result determines to increase in the mechanism in density and has kinetic factor.

The behavior of believing Ge-doped quartzy density increase is obviously different with other TERNARY GLASS discussed above.When exposing under 248nm and the 193nm excimer laser, since quartzy and boron mixes, the phosphorus doping material demonstrates low absorption under these wavelength, believe that density increase process shows as original two-photon mechanism.It is faster than what expect that Ge-doped glass has the density on the annealing point to increase.From Fig. 5 VUV spectrum, very clear, under the 193nm wavelength, glass C (20%GeO ₂Quartzy) absorption be higher than its binary system object, under the 193nm radiation, show the absorption process neutral line.The high undesiredly density of seeing increases and can be interpreted as finally causing the result of the enhancing excitation that density increases that light more effectively is coupled in the glass.

Show that it is the majorant of component that the density that the 193nm excimer laser produces increases speed, for the material at 193nm height transparent (＞70%), finding has good correlativity with the softness of the glass of representing with annealing temperature.This correlativity of finding all is correct in the family of certain component.

Table 3

To employed ANNEALING OF GLASS temperature

Sample label A B C D E

Component S iO 2(anhydrous) 7%P 2O 5/SiO 2??20％GeO 2/SiO 2??9％wtB 2O 3/SiO 2??20％B 2O 3/SiO 2

Annealing temperature K 1,423 1,231 1,323 1,073 999

Prefactor/cooperation (R^2) b=0.53 0.27/0.98 2.33/0.94 45.5/0.97 23.2/0.99 157/0.98

Table 4

For 248,193 and 157nm reach dosage with 96ppm Δ P/P, for 248 and 193nm, according to NF ²/ t calculates dosage, for 157nm, calculates dosage with NF/t

Wavelength	Dosage
		????248	????20000
????193	????4000

As discussed above, the main influence of the far ultraviolet radiation of the quartz of prolongation fusion is that density increases.Density increases the corresponding variations in refractive index of generation, and for example, the variations in refractive index that causes can be 0.0001, also finds up to 0.001.This density that causes that refractive index becomes warp increases and can be used for writing figure and for example make the Bradley grid and the waveguide scanning pattern.The applicant would rather be with the ultraviolet light that is lower than 300nm, and for example 193nm radiation utilizes with respect to the density that comes from induced absorption to increase contribution.

The applicant would rather use far ultraviolet radiation, and (the photosensitive density of the soft transparency silica glass material of optical maser wavelength＜300nm) (annealing temperature＜1350 °, transmitance＞70%) increases to produce guide structure and enclose pattern.Requirement is to guarantee to change the refractive index zone three-dimensional degree of depth that can look in the glass-based plate body at excitation wavelength quartz material substantially transparent.The representative figure of exposure is Fig. 1-3 and Fig. 8, and the optical waveguide density of making increases tunnelling device as shown in Figure 9.The variation of waveguide index increases owing to density.Situation in quartz-germanium system, preparation do not produce the oxygen defect that absorbs under excitation wavelength sample is important.

Exposure system preferably of the present invention has sufficiently high digital aperture, roughly with (D/2)/f, remains on enough little diameter d scope so that density increases the zone in Fig. 8.This back one numeral should be 10 μ m (± 5 μ m) orders of magnitude.In addition, to 10 ⁶The umber of pulse magnitude, exposure should be greater than 100mJ/cm ²Horizontal extent.This provides the variations in refractive index that favourable density increases and cause variable tolerance.

In one embodiment of the invention, single mode waveguide can write block quartz glass substrate.Under wavelength 633nm, the single mode waveguide of 5 μ m radiuses can be written into, the difference 0.001 of refractive index.The appropriate density of the boron doping soft silica glass sample D of table 3 increases and causes that variations in refractive index can use 7500[mJ/cm ²(M pulse/sec)] the dosage realization.The 1mJ output of 193nm excimer laser is directly arrived diameter 10 μ m sizes with the 200mm lens focus by the circular hole of a 5mm, adopts 220000 pulsed dosages.Under the 100Hz repetition rate, exposed about 1000 seconds.With this dosage that provides on the distance of the confocal distance (about 1000 microns) corresponding to lens, the glass substrate sample moves to form scanning pattern with the speed of 1 μ m/s.

Optical device of the present invention is illustrated in Fig. 9.Use material and the method described now, can in block glass, make multiple optical device, for example the YXing Ouheqi spare of image pattern 9 (c) expression.The present invention also can be as the star-type coupler of making the central waveguide 22 that is centered on by a plurality of peripheral waveguides 23, shown in Fig. 9 (a).The present invention also can be used for making passive Mach-Zehnder coupling mechanism, and it comprises a pair of Mach-Zehnder waveguide 26, shown in Fig. 9 (b).An active Mach-Zehnder coupling mechanism comprises the driver 24 of Mach-Zehnder waveguide 26 and heat (electric heating) or other type, shown in Fig. 9 (c), and also available method manufacturing of the present invention.The present invention also can be used at the diffraction grid of bulk manufacturing on glass Prague or other type.Shown in Fig. 9 (d).Grid line 25 is introduced in waveguide 16.Fig. 9 (E) represents the block glass optical device with first and second outer boundaries of method manufacturing of the present invention.Described first outer boundary is in first plane, and described second outer boundary is in second plane, and described second plane the and first plane are not parallel, and wherein, the waveguide core tunnel is input to the output of second outer boundary from first outer boundary.The device of Fig. 9 is to make in the method that the usefulness block on glass that flat outside basic limit is arranged density of the present invention increases, wherein the waveguide core tunnel be in uneven plane, base limit, plane on.The device of Fig. 9 be with density increasing method of the present invention by forming the waveguide tunnel passage that first, second, third refractive index has improved, wherein the 3rd tunnel passage is on the plane that separates with first, second tunnel passage.The manufacturing of Fig. 9 device comprises and forms the waveguide core tunnel passage that waveguide tunnel passage that first refractive index improved and the second adjacent refractive index have improved that wherein direct light is coupled to the second core tunnel passage from the described first core tunnel passage.Shop drawings 9 devices comprise in order to import a plurality of optical wavelength passages respectively by forming the multiplexer that a plurality of waveguide core tunnel portals separate with the wavelength that is formed with a plurality of optical wavelength passages, form multiplexed coupled zone for multichannel modulation input path and form output waveguide core tunnel for the input signal of output multichannel modulation.The line-spacing of 0.5 μ m is possible when of the present invention.

Should be appreciated that above-described preferred embodiment of the present invention admits of various changes and mutation, be interpreted as identical in the meaning and the scope of equivalence.

And then, although the element of many equivalences can here relate to, and these elements can substitute the element of describing in the preferred embodiment, and all possible equivalent that also do not meant that limit also is not limited to claim to special equivalent or the defined invention scope of composition.Those skilled in the art will appreciate that of present technique field can have other equivalence element known or that developed now, and these also should be within the spirit and scope of the present invention.

Claims (39)

1. A method for writing an optical waveguide structure inside a bulk glass substrate, characterized in that the method comprises: a) select bulk glass substrates made of soft quartz-based materials; and b) focusing the EUV laser beam onto a focal point within the material, and the focal point is moved relative to the substrate along a scan path at a scan velocity such that the density of the material along the scan path is relative to the unexposed The material is effectively enlarged while the material along the scan path is substantially free of laser-induced damage. 2. The method of claim 1, wherein selecting the bulk glass substrate comprises selecting a bulk glass substrate having a substantially uniform composition and a substantially uniform refractive index. 3. The method of claim 1, wherein the annealing humidity of the soft silica glass material is less than about 1350°K. 4. The method of claim 1, wherein the annealing humidity of the soft silica glass material is less than about 1325°K. 5. The method of claim 1, wherein said material is substantially transparent to the laser wavelength. 6. The method of claim 1, wherein the soft silica glass material comprises softening dopant doped silica glass. 7. The method of claim 1, wherein said _material comprises _a first softening dopant selected from the group _GeO2 , _{B2O3 , Al2O3} and _P2O5 . 8. The method of claim 7, wherein said material is uniformly doped with said first dopant. 9. The method of claim 1, wherein the wavelength of the laser beam is less than 250 mm. 10. The method of claim 1, wherein the wavelength of the laser beam is less than 200 mm. 11. The method of claim 7, wherein said material further comprises a second softening dopant having a composition different from said first softening dopant, wherein The aforementioned second softening dopant is selected from GeO ₂ , B ₂ O ₃ , Al ₂ O ₃ and P ₂ O ₅ groups. 12. The method of claim 1, wherein the induced density increase provides a change in refractive index of at least 1 x ^10-5 . 13. The method of claim 1, wherein the induced density increase provides a change in refractive index of at least 1 x ^10-4 . 14. The method of claim 1, wherein the glass substrate is germanium-free. 15. An optical device, characterized in that the optical device is formed by the method of claim 1. 16. A method of writing into an optical waveguide structure, comprising: a) Select a quartz substrate-like glass substrate material; Focusing laser light with a wavelength below 300nm into the substrate, moving the focus relative to the substrate along a scan path at a scan rate, so that the density of the material along the scan path is effectively increased relative to the unexposed material large, while material along said scan path is substantially free from laser-induced damage; said scan path causing an increase in refractive index is included in a bulk glass substrate with unexposed material outside the scan path An optical waveguide core is formed, providing a cladding surrounding said core forming optical waveguide. 17. The method of claim 16, wherein selecting the quartz substrate-like glass substrate material comprises selecting a glass of substantially uniform composition. 18. The method of claim 16, wherein selecting the quartz-based bulk glass substrate material comprises selecting a glass having a substantially uniform refractive index. 19. The method according to claim 18, wherein the selected glass substrate has an optical refractive index uniformity Δn≤5ppm. 20. A method of writing an optical waveguide structure in a bulk glass substrate, comprising: Selecting a _bulk glass substrate _made of a quartz substrate material doped with a dopant selected from the _B2O3 , _{Al2O3 ,} and _P2O5 groups; focusing an extreme ultraviolet laser beam inside said substrate On the focal point, the focal point is moved relative to the substrate along a scanning path at a scanning speed, so that the refractive index of the material on the scanning path is effectively increased relative to the unexposed material, and the material on the scanning path is basically There is no damage caused by laser light. 21. The method of claim 20, wherein selectively doping the quartz-based bulk glass substrate comprises softening the quartz-based material with a softening dopant. 22. The method of claim 20, wherein the annealing temperature of the selected doped quartz-based material is less than about 1350°K. 23. The method of claim 20, wherein said quartz substrate material is uniformly doped with said selected dopant. 24. The method of claim 20, wherein the quartz substrate material has an optical uniformity Δn≦50 ppm. 25. A method of manufacturing a three-dimensional structure inside a glass block, characterized in that said method comprises: providing a glass block, said glass block having an interior having a uniform composition and refractive index; providing a laser beam and lens; coupling said laser beam into said lens to form a converging focused laser beam at a focal point with an increased refractive index; positioning said focal point within said glass block and controlling relative motion between said focal point and said glass block, wherein said focal point forms an increased refractive index waveguide core within said glass block , the waveguide core with increased refractive index is used for guiding light and is surrounded by the glass block. 26. The method of claim 25, wherein said glass block has first and second outer sides, said first outer side lying in a first plane, said second outer side edge in a second plane, said second plane being non-parallel to said first plane, wherein said waveguide core traverses from an input port on said first outer side to a second outer side outlet on the side. 27. The method of claim 25, wherein said glass block has a flat outer base, and wherein said waveguide core tunnels lie in a plane that is non-parallel to said planar base. 28. The method of claim 25, comprising forming a first increased index increased density waveguide core path, a second increased index increased density waveguide core path and a third increased-index waveguide core path of increased density, wherein said third core is in a plane separate from said first and second cores. 29. The method of claim 25, wherein said providing a glass block comprises providing a glass uniformly doped with a glass softening dopant. 30. The method of claim 25, wherein said providing a glass block comprises providing a glass having a refractive index uniformity [Delta]n < 5 ppm. 31. The method of claim 25, wherein said laser beam wavelength is a lambda _laser , and said glass block has an internal transmittance of at least 50% at the wavelength of the lambda _laser . 32. The method of claim 25, wherein the focal point forms a refractive index increase of at least 1×10 ^-5 at 633 nm. 33. The method of claim 25, wherein said focal point forms a refractive index increase of at least 1 x 10 ^-4 at 633 nm. 34. The method of claim 25, wherein said providing a laser beam comprises providing an excimer laser. 35. The method of claim 25, wherein said providing a laser beam comprises providing a solid state laser. 36. The method of claim 25, wherein said providing a laser beam comprises providing a 193 nm excimer laser. 37. The method of claim 25, wherein providing a laser beam comprises providing a 248 nm excimer laser. 38. The method of claim 25, comprising forming first and second increased-index waveguide cores of increased density, wherein guided light is coupled from said first waveguide core to the second waveguide core. 39. The method according to claim 25, wherein the method comprises forming a wavelength division multiplexer for multiplexing multiple optical wavelength channels, and the forming comprises forming a plurality of waveguide core input ports , for respectively inputting a plurality of optical wavelength channels, forming a multiplexing area for multiplexing the input channels and forming an output waveguide core for outputting the multiplexing input channels.

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