[go: up one dir, main page]

EP0633953A1 - Process for reducing damage susceptibility in optical-quality crystals - Google Patents

Process for reducing damage susceptibility in optical-quality crystals

Info

Publication number
EP0633953A1
EP0633953A1 EP93908576A EP93908576A EP0633953A1 EP 0633953 A1 EP0633953 A1 EP 0633953A1 EP 93908576 A EP93908576 A EP 93908576A EP 93908576 A EP93908576 A EP 93908576A EP 0633953 A1 EP0633953 A1 EP 0633953A1
Authority
EP
European Patent Office
Prior art keywords
crystal
crystals
optical
grown
treated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP93908576A
Other languages
German (de)
French (fr)
Inventor
Patricia A. Morris
Mark G. Roelofs
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Publication of EP0633953A1 publication Critical patent/EP0633953A1/en
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/14—Phosphates

Definitions

  • This invention relates to a-process for reducing the .damage susceptibility of optically useful crystals of KTiOP0 4 and certain of its analogs.
  • EACKGRQUNP The need for optical-quality single crystals of materials exhibiting nonlinear optical properties is well established in the art.
  • Potassium titanyl phosphate i.e., KTP
  • KTP Potassium titanyl phosphate
  • KTiOP0 4 and its analogs are known to decompose upon melting, hydrothermal or flux methods have commonly been used to grow crystals of these compounds.
  • U.S. Patent No. 4,231,838 discloses a method of crystal growth from a nonaqueous flux.
  • U.S. Patent No. 3,949,323 discloses the preparation of crystals of compounds such as potassium titanyl phosphate by hydrothermal methods. Hydrothermal methods of crystal growth are considered particularly advantageous methods of crystal growth for certain applications since they often produce crystals of relatively low damage susceptibility. In part due to the popularity of the hydrothermal process, many improvements have been made in the basic process over the years.
  • U.S. Patent No. 4,305,778 discloses a high temperature hydrothermal process for crystal growth of a group of materials including potassium titanyl phosphate which utilizes a mineralizer solution comprising at least in part a stable glass composition that minimizes the tendency of the seed crystals to dissolve in the aqueous mineralizer solution before nutrient can migrate to'the seed crystals. More recently, U.S. Patent 5,066,356 discloses an improved low temperature hydrothermal process using mineralizers relatively high in potassium which produces potassium titanyl phosphate crystals at relatively low pressures, as well as low temperatures.
  • a process is provided in accordance with this invention for treating a crystal of MTiOX ⁇ 4 which has crystal structure deficiencies of M throughout the crystal, wherein M is selected from the group consisting of K, Rb, Tl and NH 4 and mixtures thereof and X is selected from the group consisting of P and As and mixtures thereof.
  • the process comprises the step of immersing said crystal in molten salt consisting essentially of at least one low melting salt of one or more monovalent cations selected from the group consisting of Rb + , K + , Cs + and Tl + , for a time sufficient to decrease the optical damage susceptibility throughout the crystal.
  • This process is considered particularly usef l for treating hydrothermally grown crystals .
  • Figure 1 is an optical absorption chart (i.e., a plot of absorption coefficient, ⁇ , versus the wavelength of incident radiation, ⁇ ) for crystals described in
  • Figure 2 is an infrared spectrum (i.e., a plot of absorption coefficient, oc, versus wavenumber, 1/ ⁇ ) for crystals described in Example I.
  • Figure 3 is an optical absorption chart for crystals described in Example II.
  • Figure 4 is an infrared spectrum for crystals described in Example II.
  • Figure 5 is an optical absorption chart for crystals described in Comparative Example A.
  • Figure 6 is an infrared spectrum for crystals described in Comparative Example A.
  • Figure 7 is an optical absorption chart for crystals described in Comparative Example B.
  • Figure 8 is an infrared spectrum for crystals described in Comparative Example B.
  • Such crystals of MT10X0 4 may have some vacant M and/or O sites in the crystal lattice or may have, particularly when hydrothermally grown, protons present in the crystal lattice. Crystals which have vacant M sites and crystals which have M sites occupied by protons are both considered deficient in M. While this invention is not bound by any theory or explanation of operation, it is believed to be those imperfections, including in particular crystal structure deficiencies of M (whether compensated for by 0 vacancies or proton presence) , that cause the susceptibility to optical damage, particularly when the crystal is hydrothermally grown. Optical damage in such crystals.can be electric field-induced and/or optical radiation-induced (e.g., laser induced).
  • the process of this invention treats crystals of TiOX ⁇ 4 which have crystal structure deficiencies of M throughout the crystal by immersing the crystals in molten salt consisting essentially of one or more salts of Rb + , K + , Cs + and/or Tl + which are low melting (i.e., melt at a temperature below the decomposition temperature of the treated crystal) . It is believed that the monovalent cation or cations from the molten low melting salt diffuse into the crystal of MTiOX0 4 , and substantially correct the crystal structure deficiencies of M, thereby reducing both electric field induced and optical radiation-induced optical damage susceptibility. It is preferred for simplicity and control of crystal composition that the monovalent cation be the same as the monovalent cation, M, in the crystal of MTiOX0 4 being treated.
  • the contact or immersion time is determined in part by the size of the crystal.
  • the treatment is particularly useful for treating crystals wherein each dimension is 0.8 millimeter or more, and typical treatment times for such crystals are at least about 2 hours. While crystals are typically contacted with the melt for several hours to a week, even longer contact times may allow for further treatment and will not generally harm the crystal.
  • While flux grown crystals may be treated by this method, the treatment is considered particularly useful for treating hydrothermally grown crystals.
  • All hydrothermally grown crystals of MTiOX ⁇ 4 can benefit from treatment in accordance with the invention. Potassium titanyl phosphate, KTiOP0 4 is preferred.
  • Typical hydrothermal crystals are grown at elevated temperature and pressure in a pressure vessel containing a means for nucleating crystal growth and a growth medium comprising a nutrient and an aqueous mineralizer solution.
  • the preferred means for nucleating crystal growth are seed crystals which provide nucleation sites.
  • seed crystals of MTiOX04 as defined above, can be utilized.
  • the low melting salt containing a monovalent cation useful in the practice of this invention should melt at a temperature below the decomposition temperature of the MTiOX ⁇ 4 . It is preferred that the low melting salt containing a monovalent cation melt at a temperature of less than about 600°C, more preferably less than about 500 C C, and most preferably less than about 475°C. Both inorganic and organic low melting salts containing a monovalent cation can be used in the practice of this invention, but inorganic low melting salts containing a monovalent cations (e.g., KNO3, KNO 2 ) are preferred for a combination of economics and availability.
  • KNO3, KNO 2 a monovalent cations
  • the melting point can be as low as 0°C, but for most practical contact times, the melting point of the low melting salt containing a monovalent cation should preferable be at least about 100°C, and, more preferably at least about 300°C. It is preferred for simplicity and control of crystal composition that the monovalent cation be the same as the monovalent cation ,M, in the hydrothermal crystal of MTiOX0 4 being treated.
  • the crystal be preheated to around the temperature of the molten salt prior to contact therewith.
  • Susceptibility of crystals to optical damage from exposure to an electric field is believed to generally correlate with susceptibility to optical damage from exposure to optical laser radiation.
  • the crystals treated in accordance with this invention have utility for frequency generation (e.g., SHG) and for electro- optic applications.
  • Example I Two samples (about 2 x 6 x 0.9 mm) were cut from the high conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOP ⁇ 4 , grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished.
  • One of the samples was placed in a KNO3 bath in a quartz crucible at 425°C for 93 hours to allow for K ion exchange.
  • the ion exchanged sample and the second sample were then damaged by being subjected to an electric field of 300 V/cm in dry air at 200°C for 20 minutes.
  • the optical absorption spectra (i.e., absorption coefficient, oc, versus wavelength, ⁇ ) of the damaged ion exchanged sample (1) , and the damaged "as- grown" sample (2), were obtained and are shown in Figure 1, along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference.
  • the data of Figure 1 clearly show the reduction in damage susceptibility for the ion exchanged KTiOP0 4 .
  • Figure 2 shows the infrared spectrum (i.e., absorption coefficient, CX, versus wavenumber, 1/ ⁇ ) of
  • Example II Two samples (about 3 x 8 x 0.9 mm) were cut from the low conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for
  • Figure 4 shows the infrared spectrum of "as-grown” (3), ion exchanged (4), and ion exchanged/damaged KTiOP ⁇ 4 (1) , indicating that the number and distribution of protons in the ion exchanged KTiOP ⁇ 4 are distinct from those of the "as-grown" or untreated KTiOP0 4 and that the damage process leaves the number and distribution of protons in the ion exchanged KTiOP ⁇ substantially unaltered.
  • Comparative Example A A z-cut sample (about 2 3 x 1 mm) was cut from the high conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOP ⁇ 4f grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished.
  • the sample was placed in a molten salt bath containing 87 mole % of KNO 3 and 13 mole % of Ba(N0 3 ) 2 bath in a quartz crucible at 425°C for 93 hours to allow for K and Ba ion exchange.
  • This Comparative Sample A was then damaged by subjection to an electrical field as described in Example I.
  • the optical absorption spectra of the damaged Comparative Sample A (1) and the damaged "as-grown" sample (2) were obtained and are shown in Figure 5, along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference.
  • a z-cut sample (about 3 x 3 x 1 mm) was cut from the low conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOP0 4 , grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished.
  • the sample was ion exchanged as described in Comparative Example A.
  • This Comparative Sample B was then damaged by subjection to an electrical field as described in Example I.
  • the optical absorption spectra of the damaged Comparative Sample B (1) and the damaged "as-grown" sample (2) were obtained and are shown in
  • Figure 1 along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference.
  • the data of Figure 7 clearly show that there was not only no reduction in damage susceptibility for the ion exchanged sample (i.e.. Comparative Sample B) but the damage susceptibility actually increased when Ba was added to the KNO 3 melt.
  • Figure 8 shows the infrared spectrum of "as-grown” (3), Comparative Sample B (4), and Comparative Sample B/damaged (1) , indicating that the crystal composition/structure of the Comparative Sample B is distinct from that of the "as-grown" or untreated KTiOP0 4 , but riot in a way which reduces the susceptibility to damage.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

A process is disclosed for treating a crystal of MTiOXO4 (wherein M is selected from the group consisting of K, Rb, Tl and NH4 and mixtures thereof and X is selected from the group consisting of P and As and mixtures thereof) which has crystal structure deficiencies of M throughout the crystal, by immersing the crystal in molten salt consisting essentially of at least one low melting salt of one or more monovalent cations selected from the group consisting of Rb?+, K+, Cs+ and Tl+¿ for a time sufficient to decrease the optical damage susceptibility throughout the crystal.

Description

PROCESS FOR REDUCING DAMAGE SUSCEPTIBILITY IN OPTICAL-QUALITY CRYSTALS FIELD OF THE INVENTION
This invention relates to a-process for reducing the .damage susceptibility of optically useful crystals of KTiOP04 and certain of its analogs.
EACKGRQUNP The need for optical-quality single crystals of materials exhibiting nonlinear optical properties is well established in the art. Potassium titanyl phosphate (i.e., KTP) is particularly useful in nonlinear optical devices, as described, for example, in U.S. Patent No. 3,949,323. For many optical applications (e.g., second harmonic and other frequency generation and electro-optic applications) optical- quality crystals having dimensions on the order of one millimeter or more are generally desired. Since KTiOP04 and its analogs are known to decompose upon melting, hydrothermal or flux methods have commonly been used to grow crystals of these compounds. U.S. Patent No. 4,231,838 discloses a method of crystal growth from a nonaqueous flux. U.S. Patent No. 3,949,323 discloses the preparation of crystals of compounds such as potassium titanyl phosphate by hydrothermal methods. Hydrothermal methods of crystal growth are considered particularly advantageous methods of crystal growth for certain applications since they often produce crystals of relatively low damage susceptibility. In part due to the popularity of the hydrothermal process, many improvements have been made in the basic process over the years. U.S. Patent No. 4,305,778 discloses a high temperature hydrothermal process for crystal growth of a group of materials including potassium titanyl phosphate which utilizes a mineralizer solution comprising at least in part a stable glass composition that minimizes the tendency of the seed crystals to dissolve in the aqueous mineralizer solution before nutrient can migrate to'the seed crystals. More recently, U.S. Patent 5,066,356 discloses an improved low temperature hydrothermal process using mineralizers relatively high in potassium which produces potassium titanyl phosphate crystals at relatively low pressures, as well as low temperatures.
While the crystals produced by the known hydrothermal processes can have high optical quality, the rigors of certain optical applications, require high resistance to optical damage or lower susceptibility to optical damage than exhibited by most hydrothermally produced crystals. For example, in uses where the crystal is subjected to high electric fields or high power laser radiation, a typical hydrothermal crystal can develop "grey tracks" or even significantly darken throughout the crystal, severely limiting the continued use of the crystal. Such damage is discussed, for example, in V. V. Lemeshko et al., Ukr. Fiz. Zh. Russ. Ed 31, No. 11:1745-50 (1986); P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104-110 (1991); and R. F. Belt et al., Proc. Soc. Photo-Opt. Instrum., Eng. 968, 100 (1988) .
SUMMARY OF THE INVENTION
A process is provided in accordance with this invention for treating a crystal of MTiOXθ4 which has crystal structure deficiencies of M throughout the crystal, wherein M is selected from the group consisting of K, Rb, Tl and NH4 and mixtures thereof and X is selected from the group consisting of P and As and mixtures thereof. The process comprises the step of immersing said crystal in molten salt consisting essentially of at least one low melting salt of one or more monovalent cations selected from the group consisting of Rb+, K+, Cs+ and Tl+, for a time sufficient to decrease the optical damage susceptibility throughout the crystal. This process is considered particularly usef l for treating hydrothermally grown crystals . BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an optical absorption chart (i.e., a plot of absorption coefficient, α, versus the wavelength of incident radiation, λ) for crystals described in
Example I.
Figure 2 is an infrared spectrum (i.e., a plot of absorption coefficient, oc, versus wavenumber, 1/λ) for crystals described in Example I. Figure 3 is an optical absorption chart for crystals described in Example II.
Figure 4 is an infrared spectrum for crystals described in Example II.
Figure 5 is an optical absorption chart for crystals described in Comparative Example A.
Figure 6 is an infrared spectrum for crystals described in Comparative Example A.
Figure 7 is an optical absorption chart for crystals described in Comparative Example B. Figure 8 is an infrared spectrum for crystals described in Comparative Example B.
All infrared spectra are for crystals cooled to less than 20°K. PSTAILEP PESCRIPTION This invention involves the discovery that crystals of MTiOXθ4 (including flux grown and hydrothermally grown crystals where M is K, Rb, Tl and/or NH4 and X is As and/or P) do not have perfect stoichiometry.
Specifically, it has been found that such crystals of MT10X04 may have some vacant M and/or O sites in the crystal lattice or may have, particularly when hydrothermally grown, protons present in the crystal lattice. Crystals which have vacant M sites and crystals which have M sites occupied by protons are both considered deficient in M. While this invention is not bound by any theory or explanation of operation, it is believed to be those imperfections, including in particular crystal structure deficiencies of M (whether compensated for by 0 vacancies or proton presence) , that cause the susceptibility to optical damage, particularly when the crystal is hydrothermally grown. Optical damage in such crystals.can be electric field-induced and/or optical radiation-induced (e.g., laser induced). The process of this invention treats crystals of TiOXθ4 which have crystal structure deficiencies of M throughout the crystal by immersing the crystals in molten salt consisting essentially of one or more salts of Rb+, K+, Cs+ and/or Tl+ which are low melting (i.e., melt at a temperature below the decomposition temperature of the treated crystal) . It is believed that the monovalent cation or cations from the molten low melting salt diffuse into the crystal of MTiOX04, and substantially correct the crystal structure deficiencies of M, thereby reducing both electric field induced and optical radiation-induced optical damage susceptibility. It is preferred for simplicity and control of crystal composition that the monovalent cation be the same as the monovalent cation, M, in the crystal of MTiOX04 being treated.
The contact or immersion time is determined in part by the size of the crystal. The treatment is particularly useful for treating crystals wherein each dimension is 0.8 millimeter or more, and typical treatment times for such crystals are at least about 2 hours. While crystals are typically contacted with the melt for several hours to a week, even longer contact times may allow for further treatment and will not generally harm the crystal.
While flux grown crystals may be treated by this method, the treatment is considered particularly useful for treating hydrothermally grown crystals. All hydrothermally grown crystals of MTiOXθ4 can benefit from treatment in accordance with the invention. Potassium titanyl phosphate, KTiOP04 is preferred. Typical hydrothermal crystals are grown at elevated temperature and pressure in a pressure vessel containing a means for nucleating crystal growth and a growth medium comprising a nutrient and an aqueous mineralizer solution. The preferred means for nucleating crystal growth are seed crystals which provide nucleation sites. In accordance with this invention seed crystals of MTiOX04, as defined above, can be utilized.
The low melting salt containing a monovalent cation useful in the practice of this invention should melt at a temperature below the decomposition temperature of the MTiOXθ4. It is preferred that the low melting salt containing a monovalent cation melt at a temperature of less than about 600°C, more preferably less than about 500CC, and most preferably less than about 475°C. Both inorganic and organic low melting salts containing a monovalent cation can be used in the practice of this invention, but inorganic low melting salts containing a monovalent cations (e.g., KNO3, KNO2) are preferred for a combination of economics and availability. The melting point can be as low as 0°C, but for most practical contact times, the melting point of the low melting salt containing a monovalent cation should preferable be at least about 100°C, and, more preferably at least about 300°C. It is preferred for simplicity and control of crystal composition that the monovalent cation be the same as the monovalent cation ,M, in the hydrothermal crystal of MTiOX04 being treated.
To avoid thermal shock to the crystal of MTiOX04 it is preferred that the crystal be preheated to around the temperature of the molten salt prior to contact therewith. Susceptibility of crystals to optical damage from exposure to an electric field is believed to generally correlate with susceptibility to optical damage from exposure to optical laser radiation. The crystals treated in accordance with this invention have utility for frequency generation (e.g., SHG) and for electro- optic applications.
Practice of the invention will become further apparent from the following non-limiting examples.
Example I Two samples (about 2 x 6 x 0.9 mm) were cut from the high conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOPθ4, grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished. One of the samples was placed in a KNO3 bath in a quartz crucible at 425°C for 93 hours to allow for K ion exchange. The ion exchanged sample and the second sample were then damaged by being subjected to an electric field of 300 V/cm in dry air at 200°C for 20 minutes. The optical absorption spectra (i.e., absorption coefficient, oc, versus wavelength, λ) of the damaged ion exchanged sample (1) , and the damaged "as- grown" sample (2), were obtained and are shown in Figure 1, along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference. The data of Figure 1 clearly show the reduction in damage susceptibility for the ion exchanged KTiOP04. Figure 2 shows the infrared spectrum (i.e., absorption coefficient, CX, versus wavenumber, 1/λ) of
"as-grown" (3), ion exchanged (4), and ion exchanged/damaged KTiOPθ4 (1) , indicating that the number and distribution of protons in the ion exchanged KTiOPθ4 are distinct from those of the "as-grown" or untreated KTiOPθ4 and that the damage process leaves the number and distribution of protons in the ion exchanged KTiOPθ4 substantially unaltered.
Example II Two samples (about 3 x 8 x 0.9 mm) were cut from the low conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for
Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOP04, grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished. One of the samples was then ion exchanged in accordance with the procedure of Example I. The ion exchanged sample and the second sample were then damaged as described in Example I. The optical absorption spectra of the damaged ion exchanged sample (1) and the damaged "as-grown" sample (2) were obtained and are shown in Figure 3, along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference. The data of Figure 3 clearly show the reduction in damage susceptibility for the ion exchanged KTiOPθ4. Figure 4 shows the infrared spectrum of "as-grown" (3), ion exchanged (4), and ion exchanged/damaged KTiOPθ4 (1) , indicating that the number and distribution of protons in the ion exchanged KTiOPθ4 are distinct from those of the "as-grown" or untreated KTiOP04 and that the damage process leaves the number and distribution of protons in the ion exchanged KTiOPθ substantially unaltered.
Comparative Example A A z-cut sample (about 2 3 x 1 mm) was cut from the high conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOPθ4f grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished. The sample was placed in a molten salt bath containing 87 mole % of KNO3 and 13 mole % of Ba(N03)2 bath in a quartz crucible at 425°C for 93 hours to allow for K and Ba ion exchange. This Comparative Sample A was then damaged by subjection to an electrical field as described in Example I. The optical absorption spectra of the damaged Comparative Sample A (1) and the damaged "as-grown" sample (2) were obtained and are shown in Figure 5, along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference. The data of Figure 5 clearly show that there was not only no reduction in damage susceptibility for the ion exchanged sample (i.e., Comparative Sample A) but the damage susceptibility actually increased when Ba was added to the KNO3 melt. Figure 6 shows the infrared spectrum of "as-grown" (3), Comparative Sample A (4), and damaged Comparative Sample A (1) indicating that the crystal composition/structure of the Comparative Sample A is distinct from that of the "as-grown" or untreated KTiOPθ4, but not in a way which reduces the susceptibility to damage. Comparative Example B
A z-cut sample (about 3 x 3 x 1 mm) was cut from the low conductivity side, as determined by measurement of the dielectric constant in accordance with P. A. Morris et al., SPIE, The International Society for Optical Engineering, Vol. 1561, Inorganic Crystals for Optics, Electro-Optics, and Frequency Conversion, 104- 110 (1991) , of a single z-cut wafer of a crystal of KTiOP04, grown by the high temperature hydrothermal process described in U.S. Patent 4,305,778, and polished. The sample was ion exchanged as described in Comparative Example A. This Comparative Sample B was then damaged by subjection to an electrical field as described in Example I. The optical absorption spectra of the damaged Comparative Sample B (1) and the damaged "as-grown" sample (2) were obtained and are shown in
Figure 1 , along with an "as-grown" or untreated sample, which was not subjected to the electric field (3) for reference. The data of Figure 7 clearly show that there was not only no reduction in damage susceptibility for the ion exchanged sample (i.e.. Comparative Sample B) but the damage susceptibility actually increased when Ba was added to the KNO3 melt. Figure 8 shows the infrared spectrum of "as-grown" (3), Comparative Sample B (4), and Comparative Sample B/damaged (1) , indicating that the crystal composition/structure of the Comparative Sample B is distinct from that of the "as-grown" or untreated KTiOP04, but riot in a way which reduces the susceptibility to damage.
The examples serve to illustrate particular embodiments of the invention. Other embodiments will become apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is understood that modifications and variations may be practiced without departing from the spirit and scope of the novel concepts of this invention. It is further understood that the invention is not confined to the particular formulations and examples herein illustrated, but it embraces such modified forms thereof as come within the scope of the following claims.

Claims

QLHMS.
1. A process for treating a crystal of MT10X04 which has crystal structural deficiencies of M throughout the crystal, wherein M is selected from the group consisting of K, Rb, Tl, NH4 and mixtures thereof and X is selected from the group consisting of P, As and mixtures thereof, comprising the step of: immersing the crystal in molten salt consisting essentially of at least one low melting salt of one or more monovalent cations selected from the group consisting of Rb+, K+, Cs+ and Tl+, for a time sufficient to decrease the optical damage susceptibility throughout the crystal.
2. The process of Claim 1 wherein the crystal is hydrothermally grown.
3. The process of Claim 1 or Claim 2 wherein each dimension of the treated crystal is 0.8 millimeter or more.
4. The process of Claim 1 or Claim 2 wherein the monovalent cation of the molten salt is the same as M in the crystal treated.
5. The process of Claim 1 or Claim 2 wherein the crystal treated is a crystal of KTiOXθ4.
6. The process of Claim 5 wherein the molten salt consists essentially of KNO3 or KNO2.
7. The process of Claim 1 or Claim 2 wherein the low melting salt melts at a temperature below about 600°C.
8. The process of Claim 1 or Claim 2 wherein the crystal being treated has M sites occupied by protons.
9. The process of Claim 1 or Claim 2 wherein the crystal being treated has vacant M sites.
EP93908576A 1992-03-31 1993-03-25 Process for reducing damage susceptibility in optical-quality crystals Ceased EP0633953A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US86083492A 1992-03-31 1992-03-31
US860834 1992-03-31
PCT/US1993/002796 WO1993020266A2 (en) 1992-03-31 1993-03-25 Process for reducing damage susceptibility in optical-quality crystals

Publications (1)

Publication Number Publication Date
EP0633953A1 true EP0633953A1 (en) 1995-01-18

Family

ID=25334133

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93908576A Ceased EP0633953A1 (en) 1992-03-31 1993-03-25 Process for reducing damage susceptibility in optical-quality crystals

Country Status (3)

Country Link
EP (1) EP0633953A1 (en)
JP (1) JPH07505355A (en)
WO (1) WO1993020266A2 (en)

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4740265A (en) * 1987-01-08 1988-04-26 E. I. Du Pont De Nemours And Company Process for producing an optical waveguide and the product therefrom

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9320266A2 *

Also Published As

Publication number Publication date
WO1993020266A3 (en) 1994-03-17
WO1993020266A2 (en) 1993-10-14
JPH07505355A (en) 1995-06-15

Similar Documents

Publication Publication Date Title
DE3789115T2 (en) METHOD FOR PRODUCING AN OPTICAL WAVE GUIDE AND PRODUCT.
Aggarwal et al. Bulk crystal growth and characterization of semiorganic nonlinear optical materials
US7101431B2 (en) Periodically poled potassium titanyl phosphate crystal
CN101799609A (en) Nonlinear optical crystal BaZnBO3F, preparation method and application thereof
Rajendran et al. Effect of pH on the growth and characterization of L-HFB single crystal
Ibanez et al. Crystal growth of a promising nonlinear optical material: 2-amino-5-nitropyridinium chloride
US5879590A (en) Low conductivity, doped KTIOPO4 and devices based thereon
US4876688A (en) Frequency doubling crystals
WO1993020266A2 (en) Process for reducing damage susceptibility in optical-quality crystals
Wang et al. Growth and properties of UV nonlinear optical crystal ZnCd (SCN) 4
Vizgert et al. Generation of the second harmonic of a neodymium laserin powders of noncentrosymmetric organic compounds
US5146533A (en) Ion exchanged crystalline waveguides and processes for their preparation
EP0633952B1 (en) Process for reducing the damage susceptibility of optical quality crystals
Daneshvar et al. Ion exchange in potassium titanyl phosphate
US5266092A (en) Processes for preparation of ion exchanged crystalline waveguides
Saji et al. 355-nm UV light generation in high-quality CsB3O5 fabricated by post-growth heat treatment
Morris et al. Gray-track damage in KTiOPO4 crystals
Hosoya et al. Nonlinear optical properties (SHG, THG) of N-(4-nitrophenyl)-L-prolinol doped alumina film prepared by a sol-gel process
CN114059169A (en) A kind of deep ultraviolet transparent sulfate crystal and optical device with ferroelectricity
Mori et al. New nonlinear optical crystal CsLiB6O10 for laser fusion
Bhuvaneswari et al. Crystallization of KDP in the presence of 4-nitro benzoic acid, L-ornithine hydrochloride and terephthalic acid
Roy Growth of large KDP and DKDP Crystals for Generation of Harmonics of Nd-Lasers
Marcy et al. Boromalate salts: a new family of solution-grown crystals for nonlinear optical applications for the UV, visible, and near-IR
Selvasekarapandian et al. Dielectric and electrical conductivity studies of flux grown KTiOPO/sub 4/and KRbTiOPO/sub 4/single crystals
Kaczmarek et al. Growth of erbium pentaphosphate monocrystals

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19940905

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE FR GB NL SE

17Q First examination report despatched

Effective date: 19950220

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19960719