Method for growing large-size CLBO crystal by using new fluxing agent

Abstract

The invention discloses a method for growing a large-size CLBO crystal by using a new fluxing agent, and belongs to the field of nonlinear optical crystals. The adopted new fluxing agent is Cs2O-Li2O-B2O3-YF3, and the large-size CLBO crystal can be obtained through growth by a high-temperature solution top oriented seed crystal growth method. According to the novel fluxing agent, the solution viscosity can be effectively reduced, and crystal defects are reduced; and the grown large-size CLBO crystal has the advantages of high transmittance, strong deliquescence resistance and the like, and can be used as a frequency doubling device of an ultraviolet laser.

Description

Technical Field

[0001] The present invention relates to the technical field of nonlinear optical crystal growth, and in particular to a method for growing large-size CLBO crystals using a new flux. Background Art

[0002] CLBO (CsLiB6O10, i.e., cesium lithium borate) crystal is a UV nonlinear optical material with excellent optical properties. It has the advantages of a large nonlinear coefficient, a small discrete angle (1.78°), a wide temperature bandwidth and acceptance angle range, and a high laser damage threshold (26GW / cm2). It has a wide range of applications in optical communications, optical imaging, high-power lasers and other fields.

[0003] CLBO crystals are typically grown using a self-fluxing Cs2O-Li2O-B2O3 system via a high-temperature solution top-directed seeding method. However, the high viscosity and growth temperature of traditional self-fluxing systems impair solution mass and heat transfer, resulting in slow crystal growth and the appearance of defects such as inclusions, making it difficult to obtain large, high-optical-quality CLBO crystals. Furthermore, the strong intrinsic hygroscopicity of CLBO crystals, which causes deliquescence cracking, also limits their engineering applications. Previous studies have reported that the simultaneous addition of molybdenum oxide and metal fluorides to the self-fluxing agent can effectively reduce viscosity and improve high-temperature solution stability. Furthermore, doping with ions such as Al3+, Yd3+, Ce3+, and Eu3+ can enhance the moisture resistance of the crystals, leading to successful growth of CLBO crystals. However, while the introduction of molybdenum oxide and alkali and alkaline earth metal fluorides reduces melt viscosity, it also inevitably produces defects such as clumps, inclusions, and clouding within the crystals, resulting in small size, low transmittance, and poor optical uniformity in the resulting CLBO crystals. While doping improves the moisture resistance of the crystal, it also brings about problems such as spectral absorption and reduces the frequency doubling conversion efficiency of the CLBO crystal.

[0004] Therefore, the present invention discloses a method for growing large-scale CLBO crystals using a novel flux. Using Cs2O, Li2O, B2O3, and YF3 as fluxes, this method uses a high-temperature solution top-directed seeding method to grow large-scale CLBO crystals with high transmittance and excellent moisture resistance. These crystals can be used as frequency-doubling devices for ultraviolet lasers. Summary of the Invention

[0005] The invention provides a method for growing large-size CLBO crystals using a novel flux.

[0006] The process involves preparing flux in the ratio of Cs2O:Li2O:B2O3:YF3 (0.8-1.2):0.8-1.2):6-6.5:0.02-0.06. The solution is then slowly cooled to room temperature and used as raw material for crystal growth. After transfer to a crystal growth furnace, CLBO crystals are grown using a top-directed seeding method using a high-temperature solution. The raw material is heated and stirred to achieve uniformity, and the saturation point of the system is determined. The crystal is then grown at a cooling rate of 0.1-0.5°C / day at the saturation point, while the seed rod is rotated synchronously to grow the crystal. Once the crystal reaches the desired size, the seed rod is slowly raised until the crystal is clear of the solution and then cooled to room temperature to produce a large-sized CLBO crystal.

[0007] The beneficial effects of the present invention are: The present invention adopts Cs2O-Li2O-B2O3-YF3 as flux to grow CLBO crystal, effectively reducing the viscosity of the flux high temperature solution and reducing crystal defects; by doping rare earth Y 3+ While improving the moisture-proof performance, a higher transmittance can be obtained. The large-sized CLBO crystal grown by the present invention has the advantages of high transmittance and high moisture-proof performance, and can be used as a frequency doubling device for ultraviolet lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 76×76×49 mm grown using the new flux in Example 2 3 large-sized crystals.

[0009] Figure 2 This is the state of the CLBO crystal grown in Example 2 after being maintained in a constant temperature of 30° C. and a constant humidity of 60% for 20 days.

[0010] Figure 3 This is the state of the CLBO crystal grown in Comparative Example 1 after being kept in a constant temperature of 30° C. and a constant humidity of 60% for 20 days. DETAILED DESCRIPTION

[0011] In order to more clearly illustrate the present invention, the following examples are used for a clearer description, but are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0012] Example 1 Weigh 3 kg of flux raw materials according to the molar ratio of Cs2O:Li2O:B2O3:YF3=1.2:1:6:0.02, mix them evenly in a weighing bag, pour them into a platinum crucible in small amounts and melt them in a high-temperature muffle furnace. After all the melting is completed, cool them to room temperature and move them to the crystal growth furnace. After the crucible with materials is moved to the crystal growth furnace, the top of the furnace mouth is sealed with an insulating furnace cover, and the small hole for the seed rod is exposed in the center of the furnace cover. The temperature is slowly raised until the raw materials are completely melted. After stirring evenly with a platinum stirring paddle, the saturation point is determined, and the C-direction seed crystal is lowered to the liquid surface at a rate of 2~4mm / min to start crystal growth. The seed rod rotates at a speed of 40~60rpm, and the cooling rate is maintained at 0.1~0.5℃ / d. After 28 days of growth, the grown crystal is slowly lifted to 2~3cm above the liquid surface and cooled to room temperature to obtain a size of 62×44×45mm. 3 Large size CLBO crystal.

[0013] Example 2 The difference between this example and Example 1 is that the molar ratio of YF3 is 0.04, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3=1.2:1:6:0.04. CLBO crystals are grown by the high-temperature solution top seeding method. The growth period is 40 days, and the crystal size is 76×76×49 mm. 3 .

[0014] Example 3 The difference between this example and Example 1 is that the molar ratio of YF3 is 0.06, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3=1.2:1:6:0.06. CLBO crystals are grown by the high-temperature solution top seeding method. The growth period is 34 days, and the crystal size is 68×58×43 mm. 3 .

[0015] Example 4 The difference between this example and Example 1 is that the molar ratio of Cs2O and Li2O is 1, the molar ratio of YF3 is 0.04, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3=1:1:6:0.04. CLBO crystals are grown by the high-temperature solution top seeding method. The growth period is 30 days, and the crystal size is 63×52×41 cm 3 .

[0016] Example 5 The difference between this example and Example 1 is that the molar ratios of Li2O and B2O3 are 0.8 and 6.5, respectively, and the molar ratio of YF3 is 0.04. 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1.2:0.8:6.5:0.04, and CLBO crystals are grown by the high-temperature solution top seeding method. The growth period is 28 days, and the crystal size is 55×43×40 cm 3 .

[0017] Example 6 The difference between this example and Example 1 is that the molar ratio of Cs2O and Li2O is 0.8, and the molar ratio of YF3 is 0.04. In this example, 3 kg of flux raw material was weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 0.8:0.8:6:0.04, and CLBO crystals were grown by the high-temperature solution top seeding method. The growth period was 26 days, and the crystal size was 61×57×43 mm. 3 .

[0018] Comparative Example 1 The difference between this example and Example 1 is that the YF3 in the flux of this comparative example is replaced with MoO3 and NaF. 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:MoO3:NaF=1:1:6:2:0.4. Other conditions are the same as those in Example 1. CLBO crystals are grown by the high-temperature solution top seeding method. The crystal growth period is 28 days, and the grown crystal size is 60×58×42 mm. 3 .

[0019] Comparative Example 2 The difference between this example and Example 1 is that the YF3 in the flux of this comparative example is replaced with MoO3 and KF. 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:MoO3:KF=1:1:6:2:0.4. Other conditions are the same as those in Example 1. CLBO crystals are grown by the high-temperature solution top seeding method. The crystal growth period is 28 days, and the grown crystal size is 56×43×38 mm. 3 .

[0020] Comparative Example 3 The difference between this example and Example 1 is that the YF3 in the flux of this comparative example is replaced by Eu2O 3， Other conditions were the same as in Example 1, and CLBO crystals were grown by the high-temperature solution top seeding method. The crystal growth period was 28 days, and the grown crystal size was 59×41×36 mm. 3 .

[0021] Comparative Example 4 The difference between this comparative example and Example 1 is that the YF3 in the flux of this comparative example is replaced by Ce2O 3， Other conditions were the same as in Example 1, and CLBO crystals were grown by the high-temperature solution top seeding method. The crystal growth period was 28 days, and the grown crystal size was 58×39×35 mm. 3 .

[0022] Comparative Example 5 The difference between this comparative example and Example 1 is that the molar ratio of YF3 is 0.005, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3=1.2:1:6:0.005. CLBO crystals are grown by the high-temperature solution top seeding method. The crystal growth period is 28 days, and the grown crystal size is 49×42×38 mm. 3 The Y ions are basically not doped into the CLBO crystal lattice.

[0023] Comparative Example 6 The difference between this comparative example and Example 1 is that the molar ratios of Cs2O and Li2O are 1 and 0.6 respectively, and the molar ratio of YF3 is 0.04. 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1:0.6:6:0.04, and CLBO crystals are grown by the high-temperature solution top seeding method. The crystal growth period is 28 days, and the grown crystal size is 38×32×29 mm. 3 The crystal growth rate decreases and the crystal optical uniformity is poor.

[0024] Comparative Example 7 The difference between this comparative example and Example 1 is that the molar ratios of Cs2O and Li2O are 1 and 1.3 respectively, and the molar ratio of YF3 is 0.04. 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1:1.3:6:0.04, and CLBO crystals are grown by the high-temperature solution top seeding method. The crystal growth period is 28 days, and the grown crystal size is 41×39×30 mm. 3 The transmittance of the grown crystal is poor.

[0025] Comparative Example 8 This comparative example differs from Example 1 in that the molar ratio of YF3 is 0.08, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1.2:1:6:0.08. Crystal creep occurs, the seed crystal is corroded, and large-sized CLBO crystals cannot be grown.

[0026] Comparative Example 9 This comparative example differs from Example 1 in that the molar ratio of Cs2O is 1.3, the molar ratio of YF3 is 0.04, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1.3:1:6:0.04. The grown crystals exhibit compositional deviations, preventing the growth of large-sized CLBO crystals.

[0027] Comparative Example 10 This comparative example differs from Example 1 in that the molar ratio of B2O3 is 7, the molar ratio of YF3 is 0.04, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1.2:1:7:0.04. The flux overflow is severe, and the viscosity is high after heating, making crystal growth difficult.

[0028] Comparative Example 11 This comparative example differs from Example 1 in that the molar ratio of Cs2O is 0.6, the molar ratio of YF3 is 0.04, and 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 0.6:1:6:0.04. The high-temperature solution has a high viscosity, and the grown CLBO crystals have defects such as inclusions.

[0029] Comparative Example 12 The difference between this comparative example and Example 1 is that the molar ratio of B2O3 is 3, and the molar ratio of YF3 is 0.04. In this comparative example, 3 kg of flux raw material is weighed according to the molar ratio of Cs2O:Li2O:B2O3:YF3 = 1:1:3:0.04. The crystals grown by the high-temperature solution top seeding method are Cs2O(B2O3)3 composite oxides, and large-sized CLBO crystals cannot be grown.

[0030] The above examples and comparative examples were subjected to comparative tests for moisture resistance and UV-visible light transmittance. The moisture resistance test involved placing the crystals at a constant temperature of 30°C and a constant humidity of 60%, recording and comparing the crystal cracking after 5, 10, 15, and 20 days. The UV-visible light transmittance also included transmittance at wavelengths of 266nm and 532nm. The results are shown in Table 1 below: Table 1. Crystal transmittance and crystal cracking under constant temperature and humidity Conclusion: The new flux was found to be more effective in growing large-scale CLBO crystals with excellent moisture resistance and transmittance within the same cycle. As the YF3 ratio gradually increased, from 0.02 to 0.04, moisture resistance improved, while UV transmittance remained unchanged. When the YF3 ratio reached 0.06, moisture resistance improved, but transmittance decreased. Increasing the YF3 concentration within an appropriate range in the Cs2O-Li2O-B2O3-YF3 flux further improved the crystal's moisture resistance and transmittance.

[0031] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for growing large-sized CLBO crystals using a new flux, characterized in that: Cs2O-Li2O-B2O3-YF3 was used as flux, and large-sized CLBO crystals were grown through the high-temperature solution top directional seeding method.

2. The flux according to claim 1, characterized in that The molar ratio of the flux Cs2O:Li2O:B2O3:YF3 is (0.8~1.2):(0.8~1.2):(6~6.5):(0.02~0.06).

3. The large-sized CLBO crystal according to claim 1 has a transmittance greater than 90% at 266 nm and 532 nm and remains intact without cracking when stored for 20 days in an environment of 30° C. and 60% humidity.

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