Rubidium titanyl phosphate electro-optical crystal and growth method thereof

Abstract

The invention provides a rubidium titanyl phosphate electro-optical crystal and a growth method thereof.The growth method of the rubidium titanyl phosphate electro-optical crystal comprises the following steps that raw material synthesis is conducted, specifically, Rb2CO3, NH4H2PO4 and TiO2 are evenly mixed according to the molar ratio, a growth raw material is synthesized through high-temperature solid-phase sintering, and the growth raw material is placed in a crucible; filling high-purity argon: putting the crucible into a crystal growth furnace, filling the high-purity argon to exhaust air for 1-3 hours, and keeping the flow of the high-purity argon constant at 1-20L / min; high-temperature reaction: performing high-temperature treatment on the growth raw material to obtain a high-temperature solution; overheating treatment: carrying out overheating treatment on the high-temperature solution to obtain an overheating solution; and crystal growth: putting a seed crystal, and growing the rubidium titanyl phosphate electro-optical crystal. Through the arrangement, the rubidium titanyl phosphate electro-optical crystal with relatively high quality can be obtained.

Description

Technical Field

[0001] The present application relates to the technical field of crystal growth, and in particular to a rubidium titanyl phosphate electro-optical crystal and a growth method thereof. Background Art

[0002] Rubidium titanyl phosphate (RbTiOPO4, RTP for short) crystal is a synthetic single crystal. In the field of laser, it can be used as a frequency doubling crystal for solid lasers in the visible and mid-infrared bands. It has the characteristics of large nonlinear coefficient, high laser damage threshold, and non-deliquescent. However, compared with the potassium titanyl phosphate (KTiOPO4, KTP for short) crystal of the same family with similar frequency doubling performance, its preparation cost is high, so its application as a frequency doubling crystal is limited. RTP crystal is also an excellent electro-optical crystal with advantages such as high electro-optical coefficient, low half-wave voltage, high laser damage threshold, and low conductivity. The electro-optical devices made of it have low insertion loss, strong environmental adaptability, good mechanical and chemical stability, and are suitable for high repetition rate operation. Therefore, RTP is a new generation of electro-optical device materials with the best comprehensive performance. It is not only used for laser ranging and irradiation, but also widely used in major international scientific exploration and detection projects, such as the "Curiosity" and "Perseverance" Mars rovers, the ATLAS laser system of the T ICESat-2 satellite, and the Laser Interferometer Gravitational Wave Observatory (LIGO).

[0003] RTP crystals are non-isotropic molten compounds. The most successful method for growing RTP electro-optical crystals is to use a modified top seed molten salt method with the aid of a polyphosphate flux. Using a flux growth system with a higher [Rb] / [P] molar ratio (R= 2.3) that is richer in Rb for crystal growth can grow RTP crystals with a more complete lattice and a closer to complete stoichiometric ratio. Growing RTP crystals in an atmospheric atmosphere is popular because of its ease of operation and low cost, but this method may result in slightly poorer crystal quality and less than ideal reproducibility. Because it still has some limitations, it is necessary to significantly improve the crystal quality by improving the growth technology, thereby improving the performance of electro-optical devices for better applications. Summary of the invention

[0004] The purpose of the present application is to provide a titanium oxyphosphate rubidium electro-optical crystal and a growth method thereof, so as to improve the quality of the titanium oxyphosphate rubidium electro-optical crystal. The specific technical solution is as follows:

[0005] The first aspect of the present application provides a method for growing a rubidium titanyl phosphate electro-optical crystal, comprising the following steps:

[0006] Raw material synthesis: Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio, sintered at high temperature to form growth raw materials, and placed in a crucible;

[0007] Filling with high-purity argon: Place the crucible in a crystal growth furnace, fill it with high-purity argon and expel the air for 1-3 hours, then set the flow rate of high-purity argon to a constant level of 1-20 L / min;

[0008] High temperature reaction: subjecting the growth raw materials to high temperature treatment to obtain a high temperature solution;

[0009] Superheating treatment: superheating the high temperature solution to obtain a superheated solution;

[0010] Crystal growth: Place seed crystal and grow rubidium titanyl phosphate electro-optical crystal.

[0011] In one embodiment of the present application, during the process of filling with argon gas, the flow rate of high-purity argon gas is kept constant at 7-16 L / min.

[0012] In one embodiment of the present application, the growth material includes solute RbTiOPO4 and solvent Rb7P3O 11 , solute RbTiOPO4 and solvent Rb7P3O 11 The mass ratio is (0.55-1.3):1.

[0013] In one embodiment of the present application, the temperature of the high temperature reaction is 870-900°C, the constant temperature time is 24-48h, and the temperature gradient of the high temperature solution is 0.3-1.5°C / cm from the center of the liquid surface downward.

[0014] In one embodiment of the present application, the temperature of the superheat treatment is 880-960° C., and the constant temperature stirring time is 36-110 h.

[0015] In one embodiment of the present application, the process of placing the seed crystal includes: cooling the superheated solution to 865-925°C at a rate of 3-15°C / h, then placing the seed crystal so that the seed crystal contacts the liquid surface, fixing the seed crystal on the seed crystal rod, keeping the temperature constant for 50-100 minutes, and then cooling to 855-905°C.

[0016] In one embodiment of the present application, the process of growing rubidium titanyl phosphate electro-optical crystals includes: cooling in the range of 905-790°C at a rate of 0.01-1.0°C / h to grow crystals for 70-105 days. After the crystal growth is completed, the grown crystals are separated from the liquid surface and cooled to 20-100°C at a rate of 10-20°C / h.

[0017] The second aspect of the present application provides a rubidium titanyl phosphate electro-optical crystal grown by the growth method provided by the first aspect of the present application, and the transmittance of the rubidium titanyl phosphate electro-optical crystal is ≥84.0%.

[0018] Beneficial effects of this application:

[0019] The present application provides a rubidium titanyl phosphate electro-optical crystal and a growth method thereof. The growth method of the rubidium titanyl phosphate electro-optical crystal comprises the following steps: raw material synthesis: Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio, and are combined into growth raw materials through high-temperature solid-phase sintering, and are placed in a crucible; high-purity argon is filled: the crucible is placed in a crystal growth furnace, high-purity argon is filled and air is exhausted for 1-3 hours, and then the flow rate of the high-purity argon is constant at 1-20L / min; high-temperature reaction: the growth raw material is subjected to high-temperature treatment to obtain a high-temperature solution; overheating treatment: the high-temperature solution is subjected to overheating treatment to obtain an overheated solution; crystal growth: a seed crystal is placed to grow the rubidium titanyl phosphate electro-optical crystal. The growth method provided in the present application provides a stable inert atmosphere environment for the titanium oxyphosphate rubidium electro-optical crystal by precisely controlling the composition and flow rate of the inert gas, so as to improve the quality of the titanium oxyphosphate rubidium electro-optical crystal, and the transmittance thereof in the wavelength range of 515-3000nm is not less than 84.0%, and the anti-laser damage threshold reaches 856MW / cm 2 @1064nm,10Hz,10ns.

[0020] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0022] Figure 1 Schematic diagram of the transmittance of the RTP crystal in Example 3. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0024] The first aspect of the present application provides a method for growing a rubidium titanyl phosphate electro-optical crystal, comprising the following steps:

[0025] Raw material synthesis: Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio, sintered at high temperature to form growth raw materials, and placed in a crucible;

[0026] Filling with high-purity argon: Place the crucible in a crystal growth furnace, fill it with high-purity argon and expel the air for 1-3 hours, then set the flow rate of high-purity argon to a constant level of 1-20 L / min;

[0027] High temperature reaction: subjecting the growth raw materials to high temperature treatment to obtain a high temperature solution;

[0028] Superheating treatment: superheating the high temperature solution to obtain a superheated solution;

[0029] Crystal growth: Place seed crystal and grow rubidium titanyl phosphate electro-optical crystal.

[0030] The growth method provided in the present application precisely controls the composition and flow rate of the inert gas so that the inert gas is high-purity argon gas. The flow rate of the high-purity argon gas during the crystal growth process is constant at 1-20L / min, providing a stable inert atmosphere environment for the titanium oxyphosphate rubidium electro-optical crystal, avoiding impurities and unnecessary chemical reactions, maintaining a stable growth environment for the titanium oxyphosphate rubidium electro-optical crystal, reducing the defects and impurities of the titanium oxyphosphate rubidium electro-optical crystal, improving the quality of the titanium oxyphosphate rubidium electro-optical crystal, and generally having better crystal growth reproducibility. The titanium oxyphosphate rubidium electro-optical crystal grown by the growth method of the present application has a transmittance of not less than 84.0% in the wavelength range of 515-3000nm, and an anti-laser damage threshold of 856MW / cm 2 @1064nm,10Hz,10ns.

[0031] In this application, the titanium phosphate rubidium electro-optical crystal is a non-isotropic molten compound, and Rb7P3O 11 As flux, Rb7P3O 11 The [Rb] / [P] molar ratio R in the flux is 2.3.

[0032] In the present application, high-purity argon refers to high-purity argon known in the art, with a purity greater than 99.99%.

[0033] Generally, the initial raw materials Rb2CO3, NH4H2PO4, and TiO2 are high-purity reagents with a purity greater than 99.7%. When the purity of the initial raw materials NH4H2PO4, Rb2CO3, and TiO2 is within the above range, the influence of impurities on the purity of the titanium oxyphosphate rubidium electro-optical crystal can be avoided, thereby improving the quality of the titanium oxyphosphate rubidium electro-optical crystal.

[0034] The present application has no particular restrictions on the particle size of the initial raw materials NH4H2PO4, Rb2CO3, and TiO2, as long as the purpose of the present application can be achieved. For example, the particle size of NH4H2PO4, Rb2CO3, and TiO2 is 1-500µm.

[0035] The present application has no particular restrictions on the temperature and holding time of high-temperature solid-phase sintering, as long as the purpose of the present application can be achieved. For example, the temperature is 830-860°C and the holding time is 2-6h.

[0036] In one embodiment of the present application, during the process of filling with argon, the flow rate of high-purity argon is kept constant at 7-16 L / min. During the growth of the titanium oxyphosphate rubidium electro-optical crystal, the flow rate of high-purity argon is kept constant within the above range, which is more conducive to providing a stable inert atmosphere environment for the titanium oxyphosphate rubidium electro-optical crystal, and is conducive to obtaining a titanium oxyphosphate rubidium electro-optical crystal with better quality.

[0037] In one embodiment of the present application, the growth material includes solute RbTiOPO4 and solvent Rb7P3O 11 , solute RbTiOPO4 and solvent Rb7P3O 11 The mass ratio of RbTiOPO4 and Rb7P3O is (0.55-1.3):1. 11 When the mass ratio is controlled within the above range, it is beneficial to synthesize the growth raw materials of titanium oxyphosphate rubidium electro-optical crystals.

[0038] In the present application, the initial raw materials Rb2CO3, NH4H2PO4, and TiO2 are weighed according to the molar ratio of Rb2CO3:NH4H2PO4:TiO2=1:2:2 and Rb2CO3:NH4H2PO4=7:6, and mixed evenly, and then sintered at high temperature to form solute RbTiOPO4 and solvent Rb7P3O 11 The solute RbTiOPO4 and the solvent Rb7P3O 11 The synthetic chemical formula is as follows:

[0039] Rb2CO3+2 NH4H2PO4+2 TiO2——>2 RbTiOPO4+CO2 +2 NH3 +3 H2O ;

[0040] 7 Rb2CO3+6 (NH4)2HPO4——>2 Rb7P3O 11 +7 CO2 +12 NH3 +9 H2O .

[0041] In one embodiment of the present application, the temperature of the high temperature reaction is 870-900°C, the constant temperature time is 24-48h, and the temperature gradient of the high temperature solution is 0.3-1.5°C / cm from the center of the liquid surface downward. When the temperature gradient of the high temperature solution is controlled within the above range from the center of the liquid surface downward, it is conducive to crystal growth and reduces energy consumption.

[0042] In one embodiment of the present application, the temperature of the superheat treatment is 880-960°C, and the constant temperature stirring time is 36-110 hours. When the liquid surface temperature and constant temperature stirring time of the superheat treatment are controlled within the above range, a clear and uniform high-temperature solution can be formed.

[0043] In one embodiment of the present application, the process of placing the seed crystal includes: cooling the superheated solution to 865-925°C at a rate of 3-15°C / h, then placing the seed crystal so that the seed crystal contacts the liquid surface, fixing the seed crystal on the seed crystal rod, and cooling to 855-905°C after keeping the temperature constant for 50-100 minutes. This process ensures that the seed crystal is slightly melted but does not break away from the contact with the melt liquid surface. When the process of placing the seed crystal is controlled in the above manner, various defects and stresses can be reduced.

[0044] In one embodiment of the present application, the process of growing a titanium oxyphosphate rubidium electro-optical crystal includes: cooling at a rate of 0.01-1.0°C / h in the range of 905-790°C to grow a crystal, the crystal growth time is 70-105 days, after the crystal growth is completed, the grown crystal is separated from the liquid surface, and the crystal is cooled to 20-100°C at a rate of 10-20°C / h. The cooling rate, temperature, and growth time during the growth of the titanium oxyphosphate rubidium electro-optical crystal are regulated within the above ranges, and the crystal can grow into a high-quality generated state crystal. After in-situ annealing heat treatment, that is, cooling the crystal to 20-100°C at a rate of 10-20°C / h, the residual stress in the crystal is reduced to a lower level, so that the quality of the crystal is further improved, and finally a complete, transparent, high-quality titanium oxyphosphate rubidium electro-optical crystal is grown.

[0045] The second aspect of the present application provides a rubidium titanyl phosphate electro-optical crystal grown by the growth method provided in the first aspect of the present application, and the transmittance of the rubidium titanyl phosphate electro-optical crystal is ≥84.0%, indicating that the rubidium titanyl phosphate electro-optical crystal has good transmittance.

[0046] Example

[0047] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods.

[0048] Test methods and equipment:

[0049] Transmittance test:

[0050] After precision polishing of the wafer with the light transmission direction in the X direction (the light transmission direction in actual application), the transmission spectrum of the crystal was tested at room temperature using an ultraviolet-visible-infrared spectrophotometer with a wavelength range of 300-6000nm.

[0051] Laser damage threshold test:

[0052] At room temperature, the laser wavelength is 1064 nm, 10 ns, 10 Hz, the incident angle is 0°, and the same power density is used to irradiate 10 test points. Each test point is irradiated with one pulse to determine the damage of each test point. According to the test methods specified in GB / T16601.1-2017 "Laser damage threshold test method for lasers and laser-related equipment Part 1 Definitions and General Principles", GB / T16601.2-2017 "Laser damage threshold test method for lasers and laser-related equipment Part 2 Threshold determination", GB / T16601.2-2017 "Laser damage threshold test method for lasers and laser-related equipment Part 3 Laser power (energy) tolerance assurance", etc., the RTP electro-optical crystal device is subjected to laser damage test.

[0053] Example 1

[0054] Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio and combined into solute RTP and solvent Rb7P3O by high temperature solid phase sintering. 11 , put RTP:Rb7P3O in a platinum crucible with a diameter of Φ160mm and a height of 150mm 11 =0.8:1 total weight 3600 grams of growth raw materials. Place the crucible in the crystal growth furnace, fill the crystal growth furnace with high-purity argon gas to exhaust the air for 1 hour, use a mass flow controller to keep the high-purity argon flow constant at 15L / min, and maintain the argon atmosphere stable until the crystal growth is completed. Raise the temperature to 875℃ to melt the growth raw materials, keep warm for 24 hours, rotate the crucible, and stir with a platinum stirrer to form a uniform and stable high-temperature solution. The temperature gradient of the high-temperature solution is 0.5℃ / cm from the center of the liquid surface downward. Continue to heat the high-temperature solution to 890℃ for superheat treatment and stir at a constant temperature for 36 hours. The superheated solution slowly drops to 875℃ at 6℃ / h, introduces a seed crystal to contact the solution surface, and keeps the temperature at a constant temperature for 60 minutes before cooling to 870℃. Then cool down and grow at a rate of 1.0℃ / h. After 80 days, the crystal growth is completed, and the generated crystal is lifted and separated from the liquid surface. The in-situ annealing heat treatment was carried out in a high-purity argon atmosphere, and the generated crystal was cooled to 60°C at a rate of 20°C / h, and finally a complete and transparent RTP crystal with a size of about 35mm×37mm×32mm was grown.

[0055] Example 2

[0056] Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio and combined into solute RTP and solvent Rb7P3O by high temperature solid phase sintering. 11 , put RTP:Rb7P3O in a platinum crucible with a diameter of Φ160mm and a height of 150mm 11=1:1 total weight of 4000 grams of raw materials. Place the crucible in a crystal growth furnace, fill the crystal growth furnace with high-purity argon gas to exhaust the air for 2 hours, use a mass flow controller to keep the high-purity argon flow constant at 8L / min, and maintain the argon atmosphere stable until the crystal growth is completed. Raise the temperature to 890℃ to melt the growth raw materials, keep warm for 48 hours, rotate the crucible, and stir with a platinum stirrer to form a uniform and stable high-temperature solution. The temperature gradient of the high-temperature solution is 1.5℃ / cm from the center of the liquid surface downward. Continue to heat the high-temperature solution to 910℃ for superheat treatment and stir at a constant temperature for 72 hours. The superheated solution slowly drops to 890℃ at 10℃ / h, introduces a seed crystal to contact the solution surface, and cools to 880℃ after a constant temperature of 75 minutes. Then cool down and grow at a rate of 0.8℃ / h. After 86 days, the crystal growth is completed, and the generated crystal is lifted and separated from the liquid surface. The in-situ annealing heat treatment was carried out in a high-purity argon atmosphere, and the generated crystal was cooled to 40°C at a rate of 15°C / h, and finally a complete and transparent RTP crystal with a size of approximately 37mm×42mm×33mm was grown.

[0057] Example 3

[0058] Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio and combined into solute RTP and solvent Rb7P3O by high temperature solid phase sintering. 11 , put RTP:Rb7P3O in a platinum crucible with a diameter of Φ160mm and a height of 150mm 11 =1.2:1 total weight of 4500 grams of raw materials. Place the crucible in a crystal growth furnace, fill the crystal growth furnace with high-purity argon gas to exhaust the air for 3 hours, use a mass flow controller to keep the argon flow constant at 10L / min, and maintain the argon atmosphere stable until the crystal growth is completed. Raise the temperature to 900℃ to melt the growth raw materials, keep warm for 36 hours, rotate the crucible, and stir with a platinum stirrer to form a uniform and stable high-temperature solution. The temperature gradient of the high-temperature solution is 1.0℃ / cm from the center of the liquid surface downward. Continue to heat the high-temperature solution to 920℃ for superheat treatment and stir at constant temperature for 100 hours. The superheated solution slowly drops to 880℃ at 15℃ / h, insert a seed crystal to contact the solution surface, keep the temperature constant for 90 minutes, and then cool to 875℃. Then cool down and grow at a rate of 0.5℃ / h. After 97 days, the crystal growth is completed, and the generated crystal is lifted and separated from the liquid surface. The resulting crystal was subjected to in-situ annealing heat treatment in a high-purity argon atmosphere, and the temperature was cooled to 30°C at a rate of 10°C / h, and finally a complete and transparent RTP crystal with a size of approximately 41mm×44mm×43mm was grown.

[0059] The preparation parameters and performance data of each embodiment are shown in Tables 1-4.

[0060] Table 1

[0061] Figure 1 The RTP crystal transmittance diagram of Example 3 is shown. Figure 1 It can be seen that the transmittance in the X direction is 84.1% at a wavelength of 532nm, the transmittance in the X direction is 85.6% at a wavelength of 1064nm, and the transmittance in the X direction is ≥84.1% in the wavelength range of 515-3000nm.

[0062] Table 2 Laser damage test data of RTP crystal prepared in Example 1

[0063] Table 3 Laser damage test data of RTP crystal prepared in Example 2

[0064] Table 4 Laser damage test data of RTP crystal prepared in Example 3

[0065] As can be seen from Tables 1-4, the transmittance of the rubidium titanyl phosphate electro-optical crystals prepared by the growth method provided by the present application in Examples 1-3 is not less than 84.0% in the wavelength range of 515-3000nm, and the laser damage threshold reaches 856MW / cm 2 @1064nm,10Hz,10ns, with high optical quality.

[0066] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for growing a titanium oxyphosphate rubidium electro-optical crystal, comprising the following steps: Raw material synthesis: Rb2CO3, NH4H2PO4 and TiO2 are uniformly mixed in molar ratio, sintered at high temperature to form growth raw materials, and placed in a crucible; Filling with high-purity argon: placing the crucible in a crystal growth furnace, filling it with high-purity argon and exhausting the air for 1-3 hours, and then setting the flow rate of the high-purity argon to a constant level of 1-20 L / min; High temperature reaction: subjecting the growth raw material to high temperature treatment to obtain a high temperature solution; Superheating: superheating the high temperature solution to obtain a superheated solution; Crystal growth: Place seed crystal and grow rubidium titanyl phosphate electro-optical crystal.

2. The growth method according to claim 1, wherein: During the process of filling with argon gas, the flow rate of the high-purity argon gas is kept constant at 7-16 L / min.

3. The growth method according to claim 1, wherein: The growth raw materials include solute RbTiOPO4 and solvent Rb7P3O 11 , the solute RbTiOPO4 and the solvent Rb7P3O 11 The mass ratio is (0.55-1.3):

1.

4. The growth method according to claim 1, wherein: The temperature of the high temperature reaction is 870-900° C., the constant temperature time is 24-48 hours, and the temperature gradient of the high temperature solution is 0.3-1.5° C. / cm from the center of the liquid surface downward.

5. The growth method according to claim 1, wherein: The temperature of the overheating treatment is 880-960° C., and the constant temperature stirring time is 36-110 hours.

6. The growth method according to claim 1, wherein: The process of placing the seed crystal includes: cooling the superheated solution to 865-925°C at a rate of 3-15°C / h, placing the seed crystal so that the seed crystal contacts the liquid surface, fixing the seed crystal on the seed crystal rod, keeping the temperature constant for 50-100 minutes, and then cooling to 855-905°C.

7. The growth method according to claim 1, wherein: The process of growing the rubidium titanyl phosphate electro-optical crystal includes: cooling in the range of 905-790°C at a rate of 0.01-1.0°C / h to grow the crystal, the time for growing the crystal is 70-105 days, after the crystal growth is completed, the grown crystal is separated from the liquid surface, and the crystal is cooled to 20-100°C at a rate of 10-20°C / h.

8. A rubidium titanyl phosphate electro-optical crystal grown according to the growth method according to any one of claims 1 to 7, wherein the transmittance of the rubidium titanyl phosphate electro-optical crystal is ≥84.0%.

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