CN117822091A - Growth method of terbium fluoride lithium magneto-optical crystal - Google Patents
Growth method of terbium fluoride lithium magneto-optical crystal Download PDFInfo
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- CN117822091A CN117822091A CN202410035698.4A CN202410035698A CN117822091A CN 117822091 A CN117822091 A CN 117822091A CN 202410035698 A CN202410035698 A CN 202410035698A CN 117822091 A CN117822091 A CN 117822091A
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- 239000013078 crystal Substances 0.000 title claims abstract description 159
- RTQINYHLCKKHTA-UHFFFAOYSA-J [F-].[Tb+3].[Li+].[F-].[F-].[F-] Chemical compound [F-].[Tb+3].[Li+].[F-].[F-].[F-] RTQINYHLCKKHTA-UHFFFAOYSA-J 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title claims abstract description 34
- 239000000203 mixture Substances 0.000 claims abstract description 31
- 239000000155 melt Substances 0.000 claims abstract description 20
- 238000001816 cooling Methods 0.000 claims abstract description 15
- 230000001681 protective effect Effects 0.000 claims abstract description 13
- 238000002156 mixing Methods 0.000 claims abstract description 11
- 239000007788 liquid Substances 0.000 claims abstract description 10
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Inorganic materials [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims abstract description 9
- 230000000630 rising effect Effects 0.000 claims abstract description 8
- 238000002844 melting Methods 0.000 claims abstract description 7
- 230000008018 melting Effects 0.000 claims abstract description 7
- 238000011010 flushing procedure Methods 0.000 claims abstract description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 24
- 239000007789 gas Substances 0.000 claims description 22
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- 229910052697 platinum Inorganic materials 0.000 claims description 12
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 7
- 229910052786 argon Inorganic materials 0.000 claims description 7
- 229910052750 molybdenum Inorganic materials 0.000 claims description 7
- 239000011733 molybdenum Substances 0.000 claims description 7
- 230000003287 optical effect Effects 0.000 abstract description 7
- 238000010438 heat treatment Methods 0.000 description 16
- 238000010521 absorption reaction Methods 0.000 description 8
- 238000001514 detection method Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000008033 biological extinction Effects 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- ATDAJGNSQPRRDT-UHFFFAOYSA-N fluoro hypofluorite terbium Chemical compound O(F)F.[Tb] ATDAJGNSQPRRDT-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 241001442654 Percnon planissimum Species 0.000 description 2
- 208000034699 Vitreous floaters Diseases 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 238000000634 powder X-ray diffraction Methods 0.000 description 2
- 238000000411 transmission spectrum Methods 0.000 description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 229910052771 Terbium Inorganic materials 0.000 description 1
- UOBPHQJGWSVXFS-UHFFFAOYSA-N [O].[F] Chemical compound [O].[F] UOBPHQJGWSVXFS-UHFFFAOYSA-N 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 239000011162 core material Substances 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 210000003128 head Anatomy 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001144 powder X-ray diffraction data Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
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
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
-
- 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
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
-
- 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
- C30B27/00—Single-crystal growth under a protective fluid
- C30B27/02—Single-crystal growth under a protective fluid by pulling from a melt
-
- 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
- C30B29/12—Halides
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/09—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on magneto-optical elements, e.g. exhibiting Faraday effect
- G02F1/093—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on magneto-optical elements, e.g. exhibiting Faraday effect used as non-reciprocal devices, e.g. optical isolators, circulators
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- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
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- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention discloses a growth method of terbium fluoride lithium magneto-optical crystals, and relates to the technical field of crystal growth. The growth method of the terbium lithium fluoride magneto-optical crystal comprises the following steps: s1: will TbF 3 Mixing with LiF to obtain a mixture; s2: placing the crucible with the mixture into a single crystal furnace, closing a furnace door, vacuumizing, and flushing protective gas; s3: controlling the temperature rising speed to completely melt the mixture, continuously rising the temperature and melting for a period of time to obtain a melt, putting the seed crystal under the liquid level of the melt to perform crystal growth, and cooling to room temperature after the crystal growth is completed to obtain the terbium lithium fluoride magneto-optical crystal. The invention is characterized in thatThe terbium lithium fluoride magneto-optical crystal prepared by the growth method has the advantages of uniform internal stress distribution and good optical uniformity.
Description
Technical Field
The invention relates to the technical field of crystal growth, in particular to a method for growing terbium fluoride lithium magneto-optical crystals.
Background
Magneto-optical devices based on the faraday effect of magneto-optical crystals, such as magneto-optical isolators, faraday rotators, and the like, have important applications in laser systems and optical communications. The magneto-optical isolator can effectively prevent the reflected light from damaging the front stage and damaging the beam quality due to the effects of unidirectional optical conduction and reflected light isolation, and is one of key devices in a high-power laser system. In recent years, with the increasing output power of solid-state lasers and fiber laser systems, the withstand power of components such as magneto-optical isolators and faraday rotators in the systems has been required to be increased. The magneto-optical crystal is a core material of a magneto-optical isolator and a Faraday rotator, and currently commercial 1 mu m-band high-power magneto-optical isolator generally adopts Terbium Gallium Garnet (TGG) crystal as a magneto-optical medium material, but the TGG crystal has large absorption loss, large thermo-optical coefficient and nonlinear coefficient and is only suitable for medium and low power lasers. In a high-power laser device with the level of hundreds of watts or more, the crystal self-absorption heating is serious, so that the change of the Verdet constant and the thermal lens effect are generated, wherein the change of the Verdet constant can seriously reduce the isolation degree of a magneto-optical isolator, and the thermal lens effect can damage the beam quality of front-stage light, thereby further causing the front-stage damage or low rear-stage amplification efficiency of a laser system and damaging the laser beam quality.
Terbium lithium fluoride (chemical formula LiTbF) 4 For short, LTF) crystal is of tetragonal scheelite structure, has a Wilde constant equivalent to TGG and extremely low absorption coefficient, is a magneto-optical crystal material with excellent performance, and is suitable for being used as a magneto-optical material of a magneto-optical device for a high-power high-energy laser system. Compared with TGG, the absorption coefficient of the LTF crystal is lower by one order of magnitude, the thermo-optic coefficient is negative, and the nonlinear coefficient is far lower than that of the TGG crystal, so that the LTF crystal is very suitable for high-power magneto-optical devices. However, LTF is a non-uniform molten compound, the crystallization process is peritectic reaction, the problem of 'floaters' formed by serious terbium oxyfluoride (TbOxF 3-2 x) is faced in the growth process, and the growth of high-quality large-size crystals is extremely difficult, and no disclosure report of large-size LTF crystals is seen in China.
Disclosure of Invention
The invention aims to provide a growth method of terbium lithium fluoride magneto-optical crystals, which solves the following technical problems:
LTF is a non-uniform molten compound, the crystallization process is peritectic reaction, and the growth process faces the problem of serious "floaters" formed by terbium oxyfluoride (TbOxF 3-2 x).
The aim of the invention can be achieved by the following technical scheme:
a growth method of terbium fluoride lithium magneto-optical crystal comprises the following steps:
s1: will TbF 3 Mixing with LiF to obtain a mixture;
s2: placing the crucible with the mixture into a single crystal furnace, closing a furnace door, vacuumizing, and flushing protective gas;
s3: controlling the temperature rising speed to completely melt the mixture, continuously rising the temperature and melting for a period of time to obtain a melt, putting the seed crystal under the liquid level of the melt to perform crystal growth, and cooling to room temperature after the crystal growth is completed to obtain the terbium lithium fluoride magneto-optical crystal.
As a further aspect of the invention: liF and TbF in S1 3 The molar ratio of (2) is 1.2-1.6:1.
As a further aspect of the invention: the crucible in S2 is a platinum crucible with 1-3 layers of molybdenum skin as a heat shield.
As a further aspect of the invention: s2, vacuumizing the single crystal furnace to 1 multiplied by 10 -4 Pa-3×10 -3 Pa; the shielding gas is argon and CF with the volume ratio of 4-9:1 4 Mixing, and charging protective gas to a pressure of 0.02MPa.
As a further aspect of the invention: tbF 3 And LiF are both 5N high purity raw materials.
As a further aspect of the invention: and S3, the seed crystal is a c-axis oriented terbium lithium fluoride crystal.
As a further aspect of the invention: the specific steps of melting in S3 are as follows: the temperature rising rate is 120-200 ℃/h, the temperature is raised to 845 ℃ to enable the mixture to be completely melted, the temperature is continuously raised to 90-120 ℃, and the temperature is kept for 4.5-5.5h.
As a further aspect of the invention: the pulling speed of the crystal growth is 0.5-2mm/h, and the rotating speed is 1-10r/min.
As a further aspect of the invention: the cooling speed after the crystal growth is completed is 15-18 ℃/h.
As a further aspect of the invention: the temperature field of the crystal growth is set up to be gradually increased by 1-2 ℃/mm in axial gradient, and the radial temperature gradient is gradually increased by 1-1.5 ℃/mm.
The invention has the beneficial effects that:
the invention firstly uses high-purity LiF and TbF with the mol ratio of 1.2-1.6:1 3 Mixing to obtain a mixture; wherein LiF and TbF 3 Is higher than terbium lithium fluoride in molar ratio of formula LiTbF 4 The stoichiometric ratio ensures that crystals are separated out in the melt with excessive LiF, effectively reduces the problem that the internal stress distribution and optical uniformity of the crystals are affected by terbium oxyfluoride (TbOxF 2-3 x) generated in the growth process because the LTF crystals are non-uniform molten compounds. Secondly, placing the crucible with the mixture into a single crystal furnace, closing a furnace door, vacuumizing, and flushing protective gas; the crystal is melted and grown in the protective gas, so that the generation of fluorine oxygen compound in the growth process is effectively reduced, and the occurrence of opaque or transparent and opaque alternate layers in the crystal is reduced. Finally, heating and melting the mixture, and continuously heating to 90-120 ℃ after the mixture is completely melted to obtain a melt; and (3) putting the seed crystal below the liquid level of the melt, and carrying out crystal growth under a certain axial temperature gradient, radial temperature gradient, lifting speed and rotating speed.
The invention controls the temperature of the melt and the temperature field to ensure that the temperature at the solid-liquid interface reaches the melting point and a certain supercooling degree exists, so that the crystal grows stably and normally. The method controls the rotating speed and the pulling speed, effectively enhances the growth stability of the interface, changes the segregation coefficient, promotes reasonable temperature gradient distribution, and increases the symmetry of the radial temperature field. The temperature field gradient provided by the invention effectively avoids the problem that the crystallization driving force is small and is not beneficial to the growth of crystals due to the fact that the temperature gradient is too small, and also avoids the problems that the temperature gradient is too large, the thermal stress of the crystals is large and the crystals are easy to crack in the crystal growth process. The growth method of terbium lithium fluoride magneto-optical crystal disclosed by the invention utilizes high-purity LiF and TbF with the molar ratio of 1.2-1.6:1 3 High purity starting materials in argon and CF 4 In the mixed growth atmosphere, reasonable temperature field gradient and melt temperature are set to form proper in-system phase change driving force to grow high-quality fluorideAnd (3) a laser crystal.
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is a graph showing the transmission spectrum of terbium lithium fluoride magneto-optical crystals prepared in example 2 of the present invention;
FIG. 2 is a powder XRD pattern of terbium lithium fluoride magneto-optical crystals prepared in example 2 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
A growth method of terbium fluoride lithium magneto-optical crystal comprises the following steps:
s1: liF (99.999% purity) and TbF were mixed in a molar ratio of 1.2:1 3 (purity 99.999%) to obtain a mixture;
s2: placing the mixture into a platinum crucible with 3 layers of molybdenum skin as heat shield, placing the platinum crucible into a single crystal furnace, closing the furnace door, and vacuumizing the single crystal furnace to 1×10 -4 PaPa, argon gas and CF with the volume ratio of 4:1 are adopted as the shielding gas 4 Mixing, and pouring protective gas until the pressure is 0.02MPa;
s3: heating to 845 ℃ at a heating rate of 120 ℃/h to enable the mixture to be completely melted, continuously heating to 90 ℃, preserving heat for 4.5h to obtain a melt, taking a c-axis directional terbium lithium fluoride crystal as seed crystal, feeding the crystal into the liquid level of the melt to perform crystal growth, maintaining the axial gradient of a temperature field to be 1 ℃/mm gradually increased, the radial temperature gradient to be 1 ℃/mm gradually increased, the pulling speed of crystal growth to be 0.5mm/h and the rotating speed to be 1r/min, controlling the cooling speed to be 15 ℃/h after the crystal growth is completed, and cooling to room temperature to obtain the terbium lithium fluoride magneto-optical crystal.
For the crystal blank prepared in the example 1, the size of the crystal blank is measured by adopting a vernier caliper, the diameter of the equal diameter part of the crystal blank is 80.12mm, the length of the equal diameter part of the crystal blank is 80.12mm, and the inside of the crystal blank is irradiated by adopting 20mWHe-Ne laser, so that no scattering particles are visible to naked eyes. The rotation angle of the LTF crystal polarization direction prepared by example 1 was 44.5 °.
Example 2
A growth method of terbium fluoride lithium magneto-optical crystal comprises the following steps:
s1: liF (99.999% purity) and TbF were mixed in a molar ratio of 1.4:1 3 (purity 99.999%) to obtain a mixture;
s2: placing the mixture into a platinum crucible with 3 layers of molybdenum skin as heat shield, placing the platinum crucible into a single crystal furnace, closing the furnace door, and vacuumizing the single crystal furnace to 1×10 -3 Pa, argon gas and CF with the volume ratio of 6:1 are used as shielding gas 4 Mixing, and pouring protective gas until the pressure is 0.02MPa;
s3: heating the temperature to 845 ℃ at a speed of 150 ℃/h to enable the mixture to be completely melted, continuously heating to 100 ℃, preserving heat for 5h to obtain a melt, taking the c-axis directional terbium lithium fluoride crystal as seed crystal, putting the crystal under the liquid level of the melt for crystal growth, maintaining the axial gradient of the temperature field to be 2 ℃/mm and increasing gradually, the radial temperature gradient to be 1.5 ℃/mm and increasing gradually, the pulling speed of crystal growth to be 1mm/h and the rotating speed to be 5r/min, controlling the cooling speed to be 15 ℃/h and cooling to room temperature after the crystal growth is completed, and obtaining the terbium lithium fluoride magneto-optical crystal.
For the crystal blank prepared in the example 2, the size of the crystal blank is measured by adopting a vernier caliper, the diameter of the equal diameter part of the crystal blank is 80.88mm and the length of the equal diameter part of the crystal blank is 80.88mm, and the interior of the crystal blank is irradiated by adopting 20mWHe-Ne laser, so that no scattering particles are visible to naked eyes. The rotation angle of the LTF crystal polarization direction prepared by example 1 was 44.9 °.
Example 3
A growth method of terbium fluoride lithium magneto-optical crystal comprises the following steps:
s1: liF (99.999% purity) and TbF were mixed in a molar ratio of 1.6:1 3 (purity 99.999%) to obtain a mixture;
s2: placing the mixture into a platinum crucible with 3 layers of molybdenum skin as heat shield, placing the platinum crucible into a single crystal furnace, closing a furnace door, and vacuumizing the single crystal furnace to 3×10 -3 Pa, protective gas isArgon, CF with volume ratio of 9:1 4 Mixing, and pouring protective gas until the pressure is 0.02MPa;
s3: heating up to 845 ℃ at a heating rate of 200 ℃/h to enable the mixture to be completely melted, continuously heating up to 120 ℃, preserving heat for 5.5h to obtain a melt, taking a c-axis directional terbium lithium fluoride crystal as seed crystal, putting the crystal into the liquid level of the melt to perform crystal growth, maintaining the axial gradient of a temperature field to be 2 ℃/mm and increasing gradually, the radial temperature gradient to be 1.5 ℃/mm and increasing gradually, the pulling speed of crystal growth to be 2mm/h and the rotating speed to be 10r/min, controlling the cooling speed to be 18 ℃/h after the crystal growth is completed, and cooling to room temperature to obtain the terbium lithium fluoride magneto-optical crystal.
For the crystal blank prepared in the example 3, the size of the crystal blank is measured by adopting a vernier caliper, the diameter of the equal diameter part of the crystal blank is 80.34mm and the length of the equal diameter part of the crystal blank is 80.34mm, and the interior of the crystal blank is irradiated by adopting 20mWHe-Ne laser, so that no scattering particles are visible to naked eyes. The rotation angle of the LTF crystal polarization direction prepared by example 1 was 44.2 °.
Comparative example 1
A growth method of terbium fluoride lithium magneto-optical crystal comprises the following steps:
s1: liF (purity 99.999%) and TbF in a molar ratio of 1:1 were combined 3 (purity 99.999%) to obtain a mixture;
s2: placing the mixture into a platinum crucible with 3 layers of molybdenum skin as heat shield, placing the platinum crucible into a single crystal furnace, closing a furnace door, and vacuumizing the single crystal furnace to 3×10 -3 Pa, argon gas and CF with the volume ratio of 9:1 are used as shielding gas 4 Mixing, and pouring protective gas until the pressure is 0.02MPa;
s3: heating up to 845 ℃ at a heating rate of 200 ℃/h to enable the mixture to be completely melted, continuously heating up to 120 ℃, preserving heat for 5.5h to obtain a melt, taking a c-axis directional terbium lithium fluoride crystal as seed crystal, putting the crystal into the liquid level of the melt to perform crystal growth, maintaining the axial gradient of a temperature field to be 2 ℃/mm and increasing gradually, the radial temperature gradient to be 1.5 ℃/mm and increasing gradually, the pulling speed of crystal growth to be 2mm/h and the rotating speed to be 10r/min, controlling the cooling speed to be 18 ℃/h after the crystal growth is completed, and cooling to room temperature to obtain the terbium lithium fluoride magneto-optical crystal.
For the crystal blank prepared in comparative example 1, the interior of the crystal blank was irradiated with 20mWHe-Ne laser, and transparent and opaque alternating layers appeared in the interior.
Comparative example 2
A growth method of terbium fluoride lithium magneto-optical crystal comprises the following steps:
s1: liF (99.999% purity) and TbF were mixed in a molar ratio of 1.4:1 3 (purity 99.999%) to obtain a mixture;
s2: placing the mixture into a platinum crucible with 3 layers of molybdenum skin as heat shield, placing the platinum crucible into a single crystal furnace, closing the furnace door, and vacuumizing the single crystal furnace to 1×10 -4 PaPa, argon gas and CF with the volume ratio of 4:1 are adopted as the shielding gas 4 Mixing, and pouring protective gas until the pressure is 0.02MPa;
s3: heating to 845 ℃ at a heating rate of 120 ℃/h to enable the mixture to be completely melted, preserving heat for 4.5h to obtain a melt, taking a c-axis directional terbium lithium fluoride crystal as a seed crystal, putting the crystal under the liquid level of the melt for crystal growth, maintaining the axial gradient of a temperature field to be increased by 1 ℃/mm, increasing the radial temperature gradient by 1 ℃/mm, controlling the pulling speed of crystal growth to be 0.5mm/h and the rotating speed to be 1r/min, controlling the cooling speed to be 15 ℃/h after the crystal growth is completed, and cooling to room temperature to obtain the terbium lithium fluoride crystal.
The crystal blank prepared in comparative example 2 had cracks.
Performance detection
(1) Referring to fig. 1, the crystal blank prepared in example 2 was cut at the head and the tail and polished at the end to obtain a crystal with a thickness of 6mm, and the crystal was tested by using a Lambda950 spectrophotometer to obtain a transmission spectrum curve. As can be seen from FIG. 1, in the 400-1500nm band, LTF crystals have a Tb at a wavelength of 489mm 3+ Outside the intrinsic absorption peak of (2), the other wave bands have high transmittance.
(2) Referring to fig. 2, the phase composition of the grown crystal was tested by powder XRD after grinding the sample taken at the wafer ingot shoulder position in example 2; as can be seen from FIG. 2, the crystalline powder XRD prepared in example 2 was compared with LiTbF 4 The diffraction peaks of the standard XRD card of the crystalline powder were in one-to-one correspondence, indicating that the crystals prepared in example 2 were free of other miscellaneous terms and were pure LFT phases.
(3) And (3) optical quality detection: 2 LTF crystal rods with the diameter of 10mm and the length of 20mm are processed from the crystal blank prepared in the embodiment 2 by using a diamond single wire cutting machine and an intangible cylindrical grinding machine, and the end faces are subjected to optical precision polishing to obtain LTF crystal elements;
according to GB/T11297.1-2017 'measuring method of wavefront distortion of laser rod', detecting by using 633nm digital wavefront interferometer; according to GB/T27661-2011 'measuring method of single-pass consumption coefficient of laser rod', a 1064mm single-pass loss test system is adopted for detection; according to GB/T11297.12-2012 (measuring method of extinction ratio of optical crystal) a extinction ratio test system is adopted for detection; the detection results are shown in Table 1;
table 1:
as is clear from Table 1, the LTF crystal element prepared in the present application has no scattering through the root, and the single pass loss coefficient is not more than 1.5% -1 The extinction ratio reaches more than 30.3 dB; the PCI weak absorption instrument is used for detecting the weak absorption coefficient of the crystals prepared in the examples 1-3 at the wavelength of 1064nm, and the test results show that the weak absorption results of the crystal elements prepared in the examples 1-3 are all less than 300ppm/cm.
The foregoing describes one embodiment of the present invention in detail, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.
Claims (9)
1. The growth method of the terbium lithium fluoride magneto-optical crystal is characterized by comprising the following steps:
s1: will TbF 3 Mixing with LiF to obtain a mixture;
s2: placing the crucible with the mixture into a single crystal furnace, closing a furnace door, vacuumizing, and flushing protective gas;
s3: controlling the temperature rising speed to completely melt the mixture, continuously rising the temperature and melting for a period of time to obtain a melt, putting the seed crystal under the liquid level of the melt to perform crystal growth, and cooling to room temperature after the crystal growth is completed to obtain the terbium lithium fluoride magneto-optical crystal.
2. The method for growing a terbium lithium fluoride magneto-optical crystal according to claim 1, wherein LiF and TbF in S1 3 The molar ratio of (2) is 1.2-1.6:1.
3. The method for growing a terbium lithium fluoride magneto-optical crystal according to claim 1, wherein the crucible in S2 is a platinum crucible having 1 to 3 layers of molybdenum skin as a heat shield.
4. The method for growing terbium lithium fluoride magneto-optical crystals according to claim 1, wherein the single crystal furnace in S2 is evacuated to 1 x 10 -4 Pa-3×10 -3 Pa; the shielding gas is argon and CF with the volume ratio of 4-9:1 4 Mixing, and charging protective gas to a pressure of 0.02MPa.
5. The method for growing a terbium lithium fluoride magneto-optical crystal according to claim 1, wherein the seed crystal in S3 is a c-axis oriented terbium lithium fluoride crystal.
6. The method for growing terbium lithium fluoride magneto-optical crystals according to claim 1, wherein the specific step of melting in S3 is: the temperature rising rate is 120-200 ℃/h, the temperature is raised to 845 ℃ to enable the mixture to be completely melted, the temperature is continuously raised to 90-120 ℃, and the temperature is kept for 4.5-5.5h.
7. The method for growing a terbium lithium fluoride magneto-optical crystal according to claim 1, wherein the pulling rate of crystal growth is 0.5-2mm/h and the rotation speed is 1-10r/min.
8. The method for growing a terbium lithium fluoride magneto-optical crystal according to claim 1, wherein the cooling rate after the crystal growth is completed is 15-18 ℃/h.
9. The method for growing terbium lithium fluoride magneto-optical crystals according to claim 1, wherein the temperature field of the crystal growth is set to be increased gradually in the axial direction by 1-2 ℃/mm and in the radial direction by 1-1.5 ℃/mm.
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