NONLINEAR OPTICAL CRYSTAL MATERIAL, METHOD FOR PREPARATION THEREOF, AND APPLICATION THEREOF

Abstract

The present application discloses a nonlinear optical crystal material, preparation method and application of the nonlinear optical crystal material. The nonlinear optical crystal material has an excellent infrared nonlinear optical performance, whose frequency-doubling intensity can reach 9.3 times of AgGaS.sub.2 with the same particle size, and it meets type-I phase matching; and its laser damage threshold can reach 7.5 times of AgGaS.sub.2 with the same particle size. The nonlinear optical crystal material has important application value in the frequency-converters which can be used for frequency doubling, sum frequency, difference frequency, optical parametric oscillation of laser in mid and far infrared waveband, and the like.

Claims

1. A nonlinear optical crystal material, whose molecular formula is
Ga.sub.2Se.sub.3 wherein the crystal structure of said nonlinear optical crystal material belongs to trigonal system, space group R3 with the lattice parameters of a=b=3˜4.2 Å, c=9˜10 Å, α=β=90°, γ=120° and Z=1.

2. A method for preparing the nonlinear optical crystal material according to claim 1, wherein after homogeneously mixing raw materials containing element gallium, and element selenium with a fluxing agent, said nonlinear optical crystal material is obtained using high temperature solid state method.

3. A method for preparing the nonlinear optical crystal material according to claim 2, wherein said fluxing agent is at least one selected from alkali metal halides, alkali earth metal halides.

4. An infrared detector, which contains said nonlinear optical crystal material according to claim 1.

5. An infrared laser, which contains said nonlinear optical crystal material according to claim 1.

6. An optical parametric oscillator, wherein the optical parametric oscillator contains, in the light path, a pump laser source, a first lens, a nonlinear optical crystal, and a second lens in this order; wherein an optical parametric oscillation chamber is formed between the first lens and the second lens; wherein the nonlinear optical crystal is at least one selected from said nonlinear optical crystal material according to claim 1.

7. The optical parametric oscillator according to claim 6, wherein the wavelength of the laser emitted by the pump laser source is in a range from 1 to 20 micrometers.

8. The optical parametric oscillator according to claim 6, wherein the area of the nonlinear optical crystal is in a range from 0.5 to 5 cm.sup.2.

9. The optical parametric oscillator according to claim 6, wherein the area of the nonlinear optical crystal is in a range from 5 to 10 cm.sup.2.

10. The optical parametric oscillator according to claim 6, wherein the output power of the optical parametric oscillator is 0.5 W or more.

11. The optical parametric oscillator according to claim 6, wherein manners for achieving phase matching in the nonlinear optical crystal by the pump laser source comprise collinear, non-collinear, critical and non-critical phase matching.

12. The optical parametric oscillator according to claim 6, wherein the pump laser source includes a liquid laser, a solid laser, a gas laser or a semiconductor laser.

13. The optical parametric oscillator according to claim 6, wherein the pump laser source includes a continuous wave laser, or a pulse laser.

14. A second harmonic generator, wherein the second harmonic generator containing one or more nonlinear optical crystal and a pump laser source; wherein the nonlinear optical crystal is said nonlinear optical crystal material according to claim 1.

15. The second harmonic generator according to claim 14, wherein the wavelength of the laser emitted by the pump laser source is in a range of from 1 to 20 micrometers.

16. The second harmonic generator according from claim 14, wherein the output power of the second harmonic generator is 0.5 W or more.

17. The second harmonic generator according to claim 14, wherein the area of the nonlinear optical crystal is in a range of from 1.0 to 5 cm.sup.2.

18. The second harmonic generator according to claim 14, wherein the area of light path on the nonlinear optical crystal is in a range from 5 to 10 cm.sup.2.

19. The second harmonic generator according to claim 14, wherein manners for achieving phase matching in the nonlinear optical crystal by the pump laser source comprise collinear, non-collinear, critical and non-critical phase matching.

20. The second harmonic generator according to claim 14, wherein the pump laser source includes a liquid laser, a solid laser, a gas laser or a semiconductor laser.

21. The second harmonic generator according to claim 14, wherein the pump laser source includes a continuous wave laser or a pulse laser.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 is X-ray powder diffraction (XRD) patterns of Sample 4.sup.#, comparing the experimental pattern with the theoretical pattern simulated from the structure of single crystal.

[0038] FIG. 2 is the crystal structure schematic of Sample 4.sup.#; wherein (a) is asymmetric unit and (b) is the structure of unit cell.

[0039] FIG. 3 is the curve of frequency-doubling intensity as a function of particle size for Sample 1.sup.#.

[0040] FIG. 4 is the UV-Vis-NIR diffuse reflectance spectrum of Sample 1.sup.#.

[0041] FIG. 5 is the infrared transmission spectrum of Sample 1.sup.#.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present application will be further described by combining with Examples. It should be understand that these Examples are only used to illustrate the present application and not to limit the scope of the present application.

Example 1 Preparation of Powder Crystal Sample

[0043] A mixture was obtained by homogeneously mixing a fluxing agent with raw materials comprising of Ga.sub.2O.sub.3, elementary substance of boron and elementary substance of selenium with the molar ratio of Ga.sub.2O.sub.3:B:Se=1:2:3. After being grinded homogeneously, the mixture was put into a quartz reactor tube; and then the quartz reactor tube was sealed by oxyhydrogen flame after being vacuumized to 10.sup.−2 Pa. And then the quartz reactor tube was put into a high temperature furnace to be heated to solid melting temperature, and then kept at the solid melting temperature for some time. And then after the temperature was reduced to 300° C. at a cooling rate of no more than 5° C./hour, stop heating and naturally cool to room temperature. After being washed by distilled water to remove the fluxing agents and being dried, the powder samples of nonlinear optical crystal material were obtained.

[0044] The sample numbers, the components of raw materials, the component and amount of the fluxing agents, solid melting temperatures and holding time at solid melting temperature are shown in Table 1.

TABLE-US-00001 TABLE 1 Holding Fluxing time at agent, mass Solid solid Components of ratio of melting melting raw material fluxing agent temper- temper- elementary to the raw ature ature Samples R.sub.2O.sub.3 substance Q material (° C.) (h) 1.sup.# Ga.sub.2O.sub.3 Se KI 850 72 3:1 2.sup.# Ga.sub.2O.sub.3 Se KI 950 24 5:1 3.sup.# Ga.sub.2O.sub.3 Se KBr 900 48 3:1

Example 2 Preparation of Single Crystal Sample

[0045] The components of raw materials and the mass ratio of fluxing agent to the raw material are same as Sample 1.sup.# at Example 1. The mixture of the raw material and the fluxing agent was grinded to be homogeneous and put into a quartz reactor tube; and then the quartz reactor tube was sealed by oxyhydrogen flame after being vacuumized to 10.sup.−2 Pa. And then the quartz reactor tube was put into a high temperature furnace to be heated to 650° C.; after being kept at 650° C. for 5 hours, the temperature was heated to 950° C. for 24 hours. And then after the temperature was reduced to 300° C. at a cooling rate of no more than 5° C./hour, stop heating and naturally cool to room temperature. After being washed by distilled water to remove the fluxing agent KI and being dried, the single crystal sample of nonlinear optical crystal material was obtained and denoted as Sample 4.sup.#.

Example 3 Structural Characterization of the Samples

[0046] The X-ray powder diffraction (XRD) patterns of Samples 1.sup.# to 4.sup.# were measured using Rigaku MiniFlex II X-ray Diffractometer with Cu target, Kα radiation source (λ=0.154184 nm). The results indicated that Samples 1.sup.# to 4.sup.# all were with high purity and high crystallinity. The typical one was the XRD pattern of Sample 4.sup.#, which was shown in FIG. 1. XRD patterns of Sample 1.sup.#, Sample 2.sup.#, Sample 3.sup.# were similar to that shown in FIG. 1, which showed that each corresponding peak had the same peak position and the ±5% difference of peak intensity, indicating that the structures of all the samples were same.

[0047] The single crystal X-ray diffraction analysis of Sample 4.sup.# was performed using Rigaku Mercury CCD X-ray Diffractometer with Mo target, Kα radiation source (λ=0.07107 nm), operated at 293K. The crystal structure was resolved by Shelxtl97. FIG. 1 is XRD pattern of Sample 4.sup.#, comparing the experimental pattern with the theoretical pattern simulated from the structure of single crystal. It showed that the experimental pattern was highly consistent with the theoretical pattern, indicating that the sample prepared was with high purity and high crystallinity.

[0048] Crystallographic Data of Sample 4.sup.# was shown in Table 2. The structures of asymmetric unit and the unit cell were shown at FIG. 2 (a) and FIG. 2 (b), respectively. In the crystal, the valences of gallium and selenium are +3 and −2, respectively. A gallium atom connects with the nearest four selenium atoms to form a GaSe.sub.4 tetrahedron, and GaSe.sub.4 tetrahedral share corners to form three-dimensional network structure.

TABLE-US-00002 TABLE 2 Crystallographic Data molecular formula Ga.sub.2Se.sub.3 molecular weight 376.32 crystal size (mm.sup.3) 0.16 × 0.14 × 0.08 Temperature (K)  293(2) Wavelength (Mo, Kα, Å) 0.71073 Space Groups trigonal system, space group R3 a (Å) 3.858(3) b (Å) 3.858(3) c (Å)  9.443(11) α = β  90° γ 120° Z 1 V (Å.sup.3) 121.72(19) density 5.134 D.sub.c (g .Math. cm.sup.−3) absorption coefficient 33.298 μ (mm.sup.−1) F(000) 164 θ range (°)□ 6.48-26.85 R1.sup.a (I > 2σ(I)) 0.0367 wR2.sup.b (all data) 0.0538 GOF on F.sup.2 0.837 Δρ.sub.max /Δρ.sub.min, e/Å.sup.3 0.721/-0.721 .sup.aR1 = ||F.sub.o| − |F.sub.c||/|F.sub.o| .sup.bwR.sup.2 = [w(F.sub.o.sup.2 − F.sub.c.sup.2).sup.2]/[w(F.sub.o.sup.2).sup.2].sup.1/2.

Example 4 Optical Properties Measurement of the Samples 1.SUP.# to 4.SUP.#

[0049] The second order nonlinear effects of Samples 1.sup.# to 4.sup.# were measured on Kurtz-Perry System. The UV-Vis-NIR diffuse reflectance spectra were measured on Perkin-Elmer Lambda 950 Ultraviolet—visible—near infrared spectrometer. The infrared transmission spectra of Samples 1.sup.# to 4.sup.# were measured on Bruker Vertex 70 infrared spectrometer.

[0050] The results indicated that Samples 1.sup.# to 4.sup.# had the similar optical properties.

[0051] The frequency-doubling intensities of Samples 1.sup.# to 4.sup.# all were over 9.3 times of AgGaS.sub.2 with the same particle size, ranging from 200 μm to 300 μm. The laser damage thresholds of Samples 1.sup.# to 4.sup.# all were over 7.5 times of commercial material AgGaS.sub.2 with the same particle size, ranging from 75 μm to 150 μm.

[0052] As typical sample, the laser-damaged threshold comparison of Sample 1.sup.# with AgGaS.sub.2 was shown in Table 3.

[0053] As a representative sample, the curve of frequency-doubling intensity as a function of particle size for Sample 1.sup.# was shown in FIG. 3, which indicated that the frequency-doubling intensity increased with the increase of particle size, showing typical type-I phase matching.

[0054] As a representative sample, the light transmittance property of Sample 1.sup.# were shown in FIG. 4 and FIG. 5, indicating the transmission region from 0.65 μm to 25 μm and the band gap of 1.90 eV.

TABLE-US-00003 TABLE 3 Laser-damaged band gap threshold Compound Space Group (eV) (MW/cm.sup.2) Sample 1.sup.# with particle size R3 1.90 4.19 range from 75 μm to 150 μm AGS with particle size range I-42d 2.52 0.558 from 75 μm to 150 μm

Example 5

[0055] The Sample 4.sup.# was subjected to directionally cutting and polishing treatment, to make an optical parametric device. A Q-switched Nd:YAG laser light source having wavelength of 1.064 μm was used as the pump light source, to produce a laser output of 3˜14 micrometers.

Example 6

[0056] The Sample 4.sup.# was subjected to directionally cutting and polishing treatment, to make an optical parametric device. A Q-switched Nd:YVO laser light source having wavelength of 1.34 μm was used as the pump source, to produce a laser output of 3˜14 micrometers.

Example 7

[0057] The Sample 4.sup.# was subjected to directionally cutting and polishing treatment, to make an optical parametric device. A Q-switched Ho:YAG laser light source having wavelength of 2.06 μm was used as the pump source, to produce a laser output of 3˜14 micrometers.

Example 8: The Performance Test of the Second Harmonic Generator

[0058] A second harmonic generator was produced using the Sample 4.sup.# as the nonlinear optical frequency conversion crystal, and a pump laser source. It was observed via output profile test that, this second harmonic generator may still produce good output profile at high output.

Example 9: The Performance Test of the Optical Parametric Oscillator

[0059] An optical parametric oscillator was produced using the Sample 4.sup.# as a nonlinear optical frequency conversion crystal, a first lens, a laser crystal, and a second lens. It was observed via output profile test that, this optical parametric oscillator may still produce good output profile at high output.

[0060] The foregoing is only several examples and preferred embodiments of the present application, and is not any kind of limit to the scope of the present application. However, it can be conceived that other variations and modifications can be made without departing from the scope covered by the claims of the present application, and all of these variations and modifications fall into the scope of protection of the present application.