Cadmium cesium bromovanadate second-order nonlinear optical crystal as well as preparation method and application thereof

Abstract

The invention discloses a cadmium cesium vanadate second-order nonlinear optical crystal and a preparation method and application thereof. The chemical formula of the cadmium cesium vanadate second-order nonlinear optical crystal is Cs2CdV2O6Br2, the molecular weight is 735.92, the space group is C mm < 2 >, and the cell parameters are as follows: a = 5.6674 (10) # imgabs 0 #, b = 18.4082 (4) # imgabs 1 #, c = 5.5668 (10) # imgabs 2 #, alpha = beta = # imgabs 3 # = 90 degrees, V = 580.766 (19) # imgabs 4 # 3, and Z = 2. The cadmium cesium bromovanadate second-order nonlinear optical crystal provided by the invention has good optical performance, the infrared optical transmission range of the crystal reaches 10 [mu] m, the crystal has a large nonlinear optical effect which can reach 12.5 * KDP (at) 1064nm and 1.5 * AGS (at) 2.1 [mu] m, phase matching can be met, high-efficiency frequency conversion output in near and middle infrared regions can be conveniently realized, and the crystal has wide application prospects. The method can be widely applied to preparation of frequency multiplication generators, frequency converters and optical parametric oscillators.

Description

Technical Field

[0001] The present invention relates to the technical field of near-infrared nonlinear optical materials, and in particular to a cesium cadmium bromovanadate second-order nonlinear optical crystal and a preparation method and application thereof. Background Art

[0002] Laser technology is one of the most important inventions after atomic energy, computers and semiconductors. It has been widely used in fiber optic communications, laser spectroscopy, lidar and weapons, laser scanning, laser surgery, laser therapy and ranging.

[0003] It is difficult to directly generate mid-infrared lasers using laser crystals and the wavelength is limited. However, the frequency conversion effect of infrared nonlinear optical crystals is an important method to obtain new mid-infrared lasers. Nonlinear optical crystals are one of the key components in solid-state lasers. They significantly expand the wavelength range of laser output through wavelength conversion technology and have therefore attracted widespread attention. To date, several excellent ultraviolet, visible and near-infrared nonlinear optical crystal materials mainly include: KBe2BO3F2 (KBBF), β -BaB2O4 (BBO), LiB3O5 (LBO) and KTiOPO4 (KTP). The more mature mid-infrared nonlinear optical crystals include ZnGeP2 and AgGaQ2 (Q = S, Se), both of which have excellent frequency doubling effect and wide mid-infrared transmission band.

[0004] However, AgGaQ2 has a relatively low laser damage threshold, and ZnGeP2 suffers from multi-phonon absorption at 1064 nm, severely limiting its high-power applications. While metal oxides typically have high laser damage thresholds and good crystal growth habits, they struggle to achieve both strong frequency doubling and a wide optical bandgap.

[0005] Therefore, there is an urgent need to develop a new near-infrared nonlinear optical material in the oxide system that has both strong frequency doubling and a wide optical band gap. Summary of the Invention

[0006] Purpose of the invention: In view of the defects of the prior art, the purpose of the present invention is to provide a cesium cadmium bromovanadate second-order nonlinear optical crystal with strong frequency doubling and wide optical band gap, as well as its preparation method and application.

[0007] Technical solution: On the one hand, the present invention provides a cesium cadmium bromovanadate second-order nonlinear optical crystal, the chemical formula of which is Cs2CdV2O6Br2, the molecular weight of which is 735.92, and the space group of which is Cmm 2. The unit cell parameters are a = 5.6674(10) , b= 18.4082(4) , c = 5.5668(10) , α = β = = 90°, V = 580.766(19) 3 , Z = 2.

[0008] The present invention adopts the strategy of element substitution with the same valence to replace the d 5 Unsaturated MnO2Cl4 with d 10 By completely replacing the saturated electronic configuration of CdO2Br4, the new compound Cs2CdV2O6Br2 was designed and successfully synthesized.

[0009] Although the space groups of Cs2CdV2O6Br2 and the parent compound are both noncentrosymmetric Cmm 2, but did not show the frequency doubling effect. However, after equivalent replacement of saturated electron elements, Cs2CdV2O6Br2 showed a strong frequency doubling effect (12.5×KDP@1064nm, 1.5×AgGaS2@2.1μm), a high laser damage threshold (80×AgGaS2@1064nm), and its infrared transmittance range also completely covered the important atmospheric window (3-5μm), providing a new solution for designing infrared oxide nonlinear optical crystals with strong frequency doubling effect, high laser damage threshold and wide spectral transparency, thus achieving the purpose of the present invention.

[0010] Another aspect of the present invention provides a method for preparing the above-mentioned cesium cadmium bromovanadate second-order nonlinear optical crystal, which is prepared by using Cs source materials, Cd source materials, V source materials and Br source materials through a solid-phase reaction method to prepare a cesium cadmium bromovanadate compound, and then growing the cadmium bromovanadate compound through a Czochralski method; or by using Cs source materials, Cd source materials, V source materials and Br source materials through a high-temperature melt solution method to prepare the cesium cadmium bromovanadate compound.

[0011] Furthermore, the Cs source material is selected from at least one of CsF, Cs2CO3, CsNO3, CsOH or CsBr; The Cd source material is selected from at least one of CdO, CdCO3, Cd(OH)2, Cd(NO3)2 or CdBr2; The V source material is selected from at least one of V2O5 and NH4VO3; The Br source material is selected from at least one of NH4Br, CsBr or CdBr2.

[0012] Furthermore, the raw materials of the cesium cadmium bromovanadate second-order nonlinear optical crystal at least include Br source material.

[0013] Specifically, the raw materials of the cesium cadmium bromovanadate second-order nonlinear optical crystal can be Cs2CO3, CdO, V2O5 and NH4Br; CdO, V2O5 and CsBr; Cs2CO3, CsBr, V2O5 and CdBr2; CsOH, CdO, V2O5 and NH4Br; Cs2CO3, CdCO3, V2O5 and NH4Br; CdCO3, V2O5 and CsBr; Cs2CO3, CdO, NH4VO3 and NH4Br.

[0014] Furthermore, the specific steps of preparing the cesium cadmium bromovanadate compound by the solid-phase reaction method are: placing a Cs source material, a Cd source material, a V source material and a Br source material in a clean mortar in proportion and grinding them for 0.5-3 hours, then placing the evenly mixed raw materials in a crucible with a diameter of 5-10 cm, placing the crucible in a programmable temperature-controlled single crystal growth furnace, heating the temperature to 340-450° C. at a rate of 10-25° C. / h for solid-phase reaction, and keeping the temperature for 1-2 days. During the holding period, the sample is taken out and ground 3-4 times, each time for half an hour, and then a powder XRD test is performed. When the measured powder XRD value is consistent with the theoretical value, the sample is placed in a furnace and kept warm for 1-2 days, and finally cooled to room temperature at a rate of 10-25° C. / h to obtain the cesium cadmium bromovanadate compound.

[0015] Furthermore, the molar ratio of Cs, Cd, V and Br in the Cs source material, Cd source material, V source material and Br source material is (2-2.5): (0.8-1.2): (1.8-2.2): (2-2.5).

[0016] Specifically, the molar ratio of Cs, Cd, V and Br is 2.2:1:2:2.2.

[0017] Furthermore, the chemical reaction formula for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal by the solid-phase reaction method can be: 1.1Cs2CO3+ CdO + V2O5+ 2.2NH4Br → Cs2CdV2O6Br2+ 1.1CO2 + NH3; CdO + V2O5+ 2.2CsBr → Cs2CdV2O6Br2; Cs2CO3+ 0.2 CsBr + V2O5+ CdBr2→ Cs2CdV2O6Br2+ 1.1CO2; 2.2CsOH + CdO + V2O5+ 2.2NH4Br → Cs2CdV2O6Br2+ 1.1H2O + 2.2NH3; 1.1Cs2CO3+ CdCO3+ V2O5+ 2.2NH4Br → Cs2CdV2O6Br2+ 2.2CO2 + 2.2NH3; CdCO3+ V2O5+ 2.2CsBr → Cs2CdV2O6Br2+ CO2; 1.1Cs2CO3+ CdO + 2NH4VO3+ 2.2NH4Br → Cs2CdV2O6Br2+ 1.1CO2 + 4.2NH3.

[0018] Furthermore, the specific steps of growing the cesium cadmium bromovanadate compound by the Czochralski method to obtain the cesium cadmium bromovanadate second-order nonlinear optical crystal are as follows: a: Grind the cesium cadmium bromovanadate compound powder, place it in a platinum crucible, heat it to 480-500°C, and keep it at this temperature for 4-6 hours to obtain a molten liquid; b: Lowering a lifting rod with a platinum wire into the molten liquid obtained in step a, and cooling it to 450-470°C at a rate of 3-5°C / h, crystallizing to obtain seed crystals at the top of the platinum wire, and then slowly cooling it to room temperature at a rate of 5-15°C / h; c. Cooling the molten liquid obtained in step a to 460-470°C at a rate of 3-5°C / h, fixing the seed crystal obtained in step b on a seed crystal rod, lowering the seed crystal from the top to contact the surface of the mixed melt or inserting the seed crystal rod into the mixed melt, rotating the seed crystal at a speed of 10-40 rpm, and growing crystals at a temperature-lowering rate of 0.2-2°C / h; d: After the single crystal grows to the desired size, the crystal is pulled upward at a speed of 1-10 mm / h to separate the crystal from the melt surface, and the temperature is lowered to room temperature at a rate of 10-30°C / h. Then, the seed crystal rod is slowly removed to obtain the cesium cadmium bromovanadate second-order nonlinear optical crystal.

[0019] Furthermore, the high-temperature melt solution method specifically comprises the following steps: placing Cs source material, Cd source material, V source material and Br source material in a clean mortar in proportion and grinding for 0.5-3 hours, then placing the evenly mixed raw materials in a crucible with a diameter of 5-10 cm, placing the crucible in a programmable temperature-controlled single crystal growth furnace, heating the temperature to 470-490° C. at a heating rate of 10-25° C. / h for a high-temperature melt solution reaction, keeping the temperature for 3-5 days, and finally cooling to room temperature at a rate of 10-25° C. / d, then selecting colorless and transparent block crystals from the crucible for single crystal XRD testing, and when the measured single crystal unit cell data is consistent with the theoretical value, the cesium cadmium bromovanadate second-order nonlinear optical crystal is obtained.

[0020] Furthermore, the molar ratio of Cs, Cd, V and Br in the Cs source material, Cd source material, V source material and Br source material is (3-6): (0.5-1.5): (4-6): (2-4).

[0021] Specifically, the molar ratio of Cs, Cd, V and Br is 4:1:5:2.

[0022] Finally, the present invention also provides the application of the above-mentioned cesium cadmium bromovanadate second-order nonlinear optical crystal in the preparation of a frequency doubling generator, a frequency converter and an optical parametric oscillator.

[0023] Specifically, the working principle of the material of the present invention in a solid-state laser is to generate at least one beam of output radiation having a frequency different from the incident electromagnetic radiation after passing at least one beam of incident electromagnetic radiation through at least one piece of cesium cadmium bromovanadate second-order nonlinear optical crystal.

[0024] Beneficial effects: (1) The cesium cadmium bromvanadate second-order nonlinear optical crystal provided by the present invention has good optical properties. Its infrared optical transmittance range reaches 10 μm. It has a large nonlinear optical effect, which can reach 12.5×KDP@1064nm and 1.5×AGS@2.1 μm. It can meet phase matching and facilitate the realization of efficient frequency conversion output in the near and mid-infrared regions.

[0025] (2) The cesium cadmium bromvanadate second-order nonlinear optical crystal provided by the present invention is a halide oxide material with good stability and can be grown in air, avoiding the cumbersome tube sealing process of traditional chalcogenides, and the crystal growth rate is relatively fast.

[0026] (3) The cesium cadmium bromovanadate second-order nonlinear optical crystal provided by the present invention can be used to manufacture mid-infrared laser frequency conversion devices, and has important uses in the fields of optics, military, laser lithography and communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The invention discloses an X-ray diffraction pattern of a polycrystalline powder of the cesium cadmium bromovanadate second-order nonlinear optical crystal and an X-ray diffraction pattern based on the structure simulation of the cesium cadmium bromovanadate second-order nonlinear optical crystal.

[0028] Figure 2 Schematic diagram of the structure of cesium cadmium bromvanadate second-order nonlinear optical crystal, where (a) is the overall structure of Cs2CdV2O6Br2 observed from the c-axis, (b) is the overall structure of Cs2CdV2O6Br2 observed from the a-axis, and (c) is [VO3] ∞ The connection mode between the chain and the [CdO2Br4] surface, (d) is a schematic diagram of the three-dimensional layer structure of Cs2CdV2O6Br2.

[0029] Figure 3Schematic diagram of the SHG effect of the cesium cadmium bromovanadate second-order nonlinear optical crystal of the present invention and the crystal in Comparative Example 1-2 in different particle size ranges.

[0030] Figure 4 (a) is the ultraviolet-visible-near-infrared diffuse reflectance spectrum of the cesium cadmium bromovanadate second-order nonlinear optical crystal of the present invention; Figure 4 (b) is the infrared analysis spectrum of the cesium cadmium bromovanadate second-order nonlinear optical crystal of the present invention.

[0031] Figure 5 This is a real picture of the cesium cadmium bromovanadate second-order nonlinear optical crystal of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be described below with reference to specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention, not to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention. Unless otherwise specified, the raw materials and equipment used in the present invention are commercially available. KDP crystals are KH2PO4 crystals; AGS crystals are AgGaS2 crystals. Example

[0033] Cadmium bromovanadate compound was prepared by solid phase reaction method by the following steps: Different Cs source materials, Cd source materials, V source materials and Br source materials were weighed in molar ratios and placed in a clean corundum mortar and ground for 1 h. Then, the evenly mixed raw materials were placed in a corundum crucible with a diameter of 10 cm. The crucible was placed in a program-controlled single crystal growth furnace and heated to 400 °C at a rate of 15 °C / h for solid-phase reaction. The temperature was kept warm for 2 days. During the holding period, the sample was taken out and ground 4 times, each time for half an hour. Then, a powder XRD test was performed. When the measured powder XRD was consistent with the theoretical value, the sample was placed in a furnace and kept warm for 1 day. Finally, it was cooled to room temperature at a rate of 20 °C / h to obtain a Cs2CdV2O6Br2 compound.

[0034] The selection of the raw materials and their molar ratios are shown in Table 1 below:

[0035] Table 1 Example

[0036] The cesium cadmium bromovanadate second-order nonlinear optical crystal was prepared by a high-temperature melt solution method by the following steps: Different Cs source materials, Cd source materials, V source materials and Br source materials were weighed in molar ratios and placed in a clean corundum mortar and ground for 1 hour. The evenly mixed raw materials were then placed in a corundum crucible with a diameter of 10 cm. The crucible was placed in a programmable temperature-controlled single crystal growth furnace and heated to 480 °C at a heating rate of 25 °C / h for high-temperature melt solution reaction. The temperature was kept at this temperature for 2 days and finally cooled to room temperature at a rate of 20 °C / d. Then, colorless and transparent block crystals were selected from the crucible for single crystal XRD testing. When the measured single crystal unit cell data were consistent with the theoretical value, it was determined that cesium cadmium bromovanadate second-order nonlinear optical crystals were obtained.

[0037] The selection of the raw materials and their molar ratios are shown in Table 2 below:

[0038] Table 2 Example

[0039] The cesium cadmium bromovanadate second-order nonlinear optical crystal was prepared by Czochralski crystal growth in the following steps: a: The Cs2CdV2O6Br2 compound powders prepared in Experiment No. 1 and Experiment No. 2 were ground, placed in a platinum crucible, and heated to 500°C for 6 hours to obtain a molten liquid; b: Lowering a lifting rod with a platinum wire into the molten liquid obtained in step a, and cooling it to 470°C at a rate of 5°C / h, crystallizing a seed crystal at the top of the platinum wire, and then slowly cooling it to room temperature at a rate of 10°C / h; c) Cooling the molten liquid obtained in step a to 460°C at a rate of 5°C / h, fixing the seed crystal obtained in step b on the seed crystal rod, lowering the seed crystal from the top to contact the surface of the mixed melt, rotating the seed crystal at a speed of 30 r / min, and growing the crystal under the condition of cooling the temperature at a rate of 1°C / h; d: After the single crystal grows to the desired size, the crystal is pulled upward at a speed of 5 mm / h to separate the crystal from the melt surface, and the temperature is lowered to room temperature at a rate of 20°C / h. Then, the seed crystal rod is slowly removed to obtain the cesium cadmium bromovanadate second-order nonlinear optical crystal.

[0040] Comparative Example 1 KDP crystal.

[0041] Comparative Example 2 AGS crystal.

[0042] Performance Testing 1. The Cs2CdV2O6Br2 compound prepared in Example 1 and the cesium cadmium bromovanadate second-order nonlinear optical crystals prepared in Examples 2 and 3 were tested. The test results are as follows: Figure 1 and Figure 2As shown. Among them, Figure 1 The XRD pattern and simulated diffraction pattern of Cs2CdV2O6Br2 compound are shown below. Figure 2 Schematic diagram of the structure of cesium cadmium bromovanadate second-order nonlinear optical crystal.

[0043] 2. The SHG effect of the crystals of Examples 2-3 and Comparative Examples 1-2 in different particle size ranges was tested. The test results are as follows: Figure 3 Among them, Cs2CdV2O6Br2 exhibits a larger SHG response, which is about 12.5 times that of KDP and 1.5 times that of AGS.

[0044] 3. The spectrum data of the cesium cadmium bromovanadate second-order nonlinear optical crystal obtained in Example 2-3 was tested. The test results are as follows: Figure 4 As shown. Figure 4 (a) is the UV-visible-near-infrared diffuse reflectance spectrum of the cesium cadmium bromovanadate second-order nonlinear optical crystal of the present invention. Cs2CdV2O6Br2 has a large optical band gap, and the UV cutoff edge reaches 386 nm; Figure 4 (b) is the infrared analysis spectrum of the cesium cadmium bromovanadate second-order nonlinear optical crystal of the present invention. The infrared transmission spectrum of the Cs2CdV2O6Br2 crystal shows five absorption peaks: 963 and 909 cm -1 The peak at 676 cm is attributed to the stretching vibration of the short V=O bond or VO bond. -1 The peak at 873 cm corresponds to the stretching vibration of the VO bond, while the peaks at 510 cm -1 The peak at is related to the bending vibration of VOV; the infrared absorption edge of Cs2CdV2O6Br2 reaches 10.4 μm, covering the important atmospheric window (3-5 μm).

[0045] The above embodiments are only for illustrating the technical concept and features of the present invention. Its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. It cannot be used to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cesium cadmium bromovanadate second-order nonlinear optical crystal, characterized in that: The chemical formula is Cs2CdV2O6Br2, the molecular weight is 735.92, and the space group is Cmm 2. The unit cell parameters are a = 5.6674(10) , b = 18.4082(4) , c = 5.5668(10) , α = β = = 90°, V = 580.766(19) 3 , Z = 2.

2. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 1, characterized in that: The method is prepared by preparing cesium cadmium bromovanadate compound through solid phase reaction of Cs source material, Cd source material, V source material and Br source material and then growing crystal through Czochralski method; or by preparing Cs source material, Cd source material, V source material and Br source material through high temperature melt solution method.

3. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 2, characterized in that: The Cs source material is selected from at least one of CsF, Cs2CO3, CsNO3, CsOH or CsBr; The Cd source material is selected from at least one of CdO, CdCO3, Cd(OH)2, Cd(NO3)2 or CdBr2; The V source material is selected from at least one of V2O5 and NH4VO3; The Br source material is selected from at least one of NH4Br, CsBr or CdBr2.

4. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 2, wherein: The specific steps of preparing the cesium cadmium bromovanadate compound by the solid-phase reaction method are as follows: placing a Cs source material, a Cd source material, a V source material, and a Br source material in a clean mortar according to proportion, grinding for 0.5-3 hours, then placing the evenly mixed raw materials in a crucible with a diameter of 5-10 cm, placing the crucible in a programmable temperature-controlled single crystal growth furnace, heating the temperature to 340-450° C. at a heating rate of 10-25° C. / h to carry out a solid-phase reaction, and keeping the temperature for 1-2 days. During the holding period, the sample is taken out and ground 3-4 times, each time for half an hour, and then a powder XRD test is carried out. When the measured powder XRD value is consistent with the theoretical value, the sample is placed in a furnace and kept warm for 1-2 days, and finally cooled to room temperature at a rate of 10-25° C. / h to prepare the cesium cadmium bromovanadate compound.

5. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 4, characterized in that: The molar ratio of Cs, Cd, V and Br in the Cs source material, Cd source material, V source material and Br source material is (2-4): (0.5-1.5): (1.5-2.5): (2-3).

6. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 2, wherein: The specific steps of preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal by growing the cesium cadmium bromovanadate compound by the Czochralski method are as follows: a: Grind the cesium cadmium bromovanadate compound powder, place it in a platinum crucible, heat it to 480-500°C, and keep it at this temperature for 4-6 hours to obtain a molten liquid; b: Lowering a lifting rod with a platinum wire into the molten liquid obtained in step a, and cooling it to 450-470°C at a rate of 3-5°C / h, crystallizing to obtain seed crystals at the top of the platinum wire, and then slowly cooling it to room temperature at a rate of 5-15°C / h; c. Cooling the molten liquid obtained in step a to 460-470°C at a rate of 3-5°C / h, fixing the seed crystal obtained in step b on a seed crystal rod, lowering the seed crystal from the top to contact the surface of the mixed melt or inserting the seed crystal rod into the mixed melt, rotating the seed crystal at a speed of 10-40 rpm, and growing crystals at a temperature-lowering rate of 0.2-2°C / h; d: After the single crystal grows to the desired size, the crystal is pulled upward at a speed of 1-10 mm / h to separate the crystal from the melt surface, and the temperature is lowered to room temperature at a rate of 10-30°C / h. Then, the seed crystal rod is slowly removed to obtain the cesium cadmium bromovanadate second-order nonlinear optical crystal.

7. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 2, wherein: The high-temperature melt solution method specifically comprises the following steps: placing Cs source material, Cd source material, V source material, and Br source material in a clean mortar in proportion and grinding for 0.5-3 hours; then placing the evenly mixed raw materials in a crucible with a diameter of 5-10 cm; placing the crucible in a programmable temperature-controlled single crystal growth furnace; heating the temperature to 470-490° C. at a rate of 10-25° C. / h for a high-temperature melt solution reaction; maintaining the temperature for 3-5 days; and finally cooling to room temperature at a rate of 10-25° C. / d; then selecting colorless and transparent block crystals from the crucible for single crystal XRD testing; and when the measured single crystal unit cell data is consistent with the theoretical value, the cesium cadmium bromovanadate second-order nonlinear optical crystal is obtained.

8. The method for preparing the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 7, characterized in that: The molar ratio of Cs, Cd, V and Br in the Cs source material, Cd source material, V source material and Br source material is (3-6): (0.5-1.5): (4-6): (2-4).

9. Use of the cesium cadmium bromovanadate second-order nonlinear optical crystal according to claim 1 in the preparation of a frequency doubling generator, a frequency converter and an optical parametric oscillator.

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