NONLINEAR OPTICAL CRYSTAL, METHOD FOR PREPARING THE SAME AND APPLICATION THEREOF

Abstract

Disclosed in the present invention is a nonlinear optical crystal. The chemical formula of the nonlinear optical crystal is MHgGeSe.sub.4, M being selected from Ba or Sr. The nonlinear optical crystal has no symmetrical center, belongs to an orthorhombic crystal system, and has a space group Ama2. The nonlinear optical crystal is an infrared nonlinear optical crystal, and has the advantages of great nonlinear optical effect, wide light transmitting band, high hardness, good mechanical properties, breakage resistance, deliquescence resistance, easiness in processing and preserving, etc. Also disclosed in the present invention are a method for preparing the nonlinear optical crystal and application thereof.

Claims

1. A nonlinear optical crystal, wherein the chemical formula of the nonlinear optical crystal is MHgGeSe.sub.4, where M is selected from Ba or Sr; the nonlinear optical crystal has no symmetrical center, belongs to an orthorhombic crystal system, and has a space group Ama2.

2. The nonlinear optical crystal according to claim 1, wherein when M is Ba, the cell parameters of the nonlinear optical crystal are as follows: a=11.255Å, b=11.033Å, c=6.685Å, α=β=γ=90°, Z=4; when M is Sr, the cell parameters of the nonlinear optical crystal are as follows: a=10.8345Å, b=10.7441Å, c=6.6392Å, α=β=γ=90°, Z=4.

3. A method for preparing the nonlinear optical crystal according to claim 1, wherein the nonlinear optical crystal is prepared by adopting a high-temperature melt spontaneous crystallization method, and the method specifically comprises the following steps: heating a mixture with a component equivalent to MHgGeSe.sub.4 or a powdered MHgGeSe.sub.4 compound till complete melting, performing heat preservation to obtained high-temperature solution and then performing cooling to room temperature to obtain the nonlinear optical crystal, where M is selected from Ba or Sr.

4. The method for preparing the nonlinear optical crystal according to claim 3, wherein the time of heat preservation is 24-96 h; the cooling speed is 1-10° C./h.

5. The method for preparing the nonlinear optical crystal according to claim 1, wherein the nonlinear optical crystal is prepared by adopting a crucible descending method, a mixture with a component equivalent to MHgGeSe.sub.4 or a powdered MHgGeSe.sub.4 compound is placed in a crystal growing device, heating is performed till complete melting, the crystal growing device is vertically descended, and crystallization is realized in a vertical descending process to obtain the nonlinear optical crystal, where M is selected from Ba or Sr.

6. The method for preparing the nonlinear optical crystal according to claim 5, wherein the vertical descending speed is 0.1-10 mm/h and the time is 5-20 d.

7. The method for preparing the nonlinear optical crystal according to claim 3, wherein the mixture with a component equivalent to MHgGeSe.sub.4 is obtained by mixing raw materials containing elements M, Hg, Ge and Se, and the molar ratio of M:Hg:Ge:Se is 1:1:1:4.

8. The method for preparing the nonlinear optical crystal according to claim 3, wherein in the raw materials, M comes from elemental M or MSe; Hg comes from Hg or HgSe; Ge comes from Ge, GeSe or GeSe.sub.2; Se comes from elemental Se, MSe, HgSe, GeSe or GeSe.sub.2.

9. The method for preparing the nonlinear optical crystal according to claim 3, wherein a method for preparing the powdered MHgGeSe.sub.4 compound comprises: uniformly mixing raw materials containing elements M, Hg, Ge and Se according to the molar ratio 1:1:1:4 of M:Hg:Ge:Se, performing heating to 600-1150° C. for solid phase reaction, and performing grinding to obtain the powdered MHgGeSe.sub.4 compound; preferably, in the raw materials, M comes from elemental M or SrSe; Hg comes from Hg or HgSe; Ge comes from Ge, GeSe or GeSe.sub.2; Se comes from elemental Se, MSe, HgSe, GeSe or GeSe.sub.2.

10. Application of the nonlinear optical crystal according to claim 1 in preparation of a nonlinear optical device.

11. The application according to claim 10, wherein the nonlinear optical device comprises a device for passing at least one beam of incident electromagnetic radiation through at least one nonlinear optical crystal to generate at least one beam of output radiation with frequency different from the frequency of the incident electromagnetic radiation.

12. The method for preparing the nonlinear optical crystal according to claim 5, wherein the mixture with a component equivalent to MHgGeSe.sub.4 is obtained by mixing raw materials containing elements M, Hg, Ge and Se, and the molar ratio of M:Hg:Ge:Se is 1:1:1:4.

13. The method for preparing the nonlinear optical crystal according to claim 5, wherein in the raw materials, M comes from elemental M or MSe; Hg comes from Hg or HgSe; Ge comes from Ge, GeSe or GeSe.sub.2; Se comes from elemental Se, MSe, HgSe, GeSe or GeSe.sub.2.

14. The method for preparing the nonlinear optical crystal according to claim 5, wherein a method for preparing the powdered MHgGeSe.sub.4 compound comprises: uniformly mixing raw materials containing elements M, Hg, Ge and Se according to the molar ratio 1:1:1:4 of M:Hg:Ge:Se, performing heating to 600-1150° C. for solid phase reaction, and performing grinding to obtain the powdered MHgGeSe.sub.4 compound; preferably, in the raw materials, M comes from elemental M or SrSe; Hg comes from Hg or HgSe; Ge comes from Ge, GeSe or GeSe.sub.2; Se comes from elemental Se, MSe, HgSe, GeSe or GeSe.sub.2.

Description

DESCRIPTION OF THE DRAWINGS

[0048] The specific examples of the present application will be further described below in detail with reference to the drawings.

[0049] FIG. 1 illustrates a structural schematic view of a nonlinear optical crystal SrHGeSe.sub.4 prepared in example 1 of the present application.

[0050] FIG. 2 illustrates a structural schematic view of a nonlinear optical crystal BaHgGeSe.sub.4 prepared in example 5 of the present application.

[0051] FIG. 3 illustrates a working principle diagram of a nonlinear optical device obtained by adopting a nonlinear optical crystal according to one example of the present application. In the drawings: 1-laser, 2-incident laser beam, 3-nonlinear optical crystal after crystal post-treatment and optical processing, 4-generated emergent laser beam, 5-filter.

DESCRIPTION OF THE EMBODIMENTS

[0052] In order to more clearly describe the present application, the present application will be further described below in combination with the preferred examples with reference to the drawings. Similar parts in the drawings are represented by the same reference signs. Those skilled in the art should understand that the content specifically described below is descriptive rather than restrictive, and should not limit the scope of protection of the present application.

EXAMPLE 1

[0053] A SrHgGeSe.sub.4 nonlinear optical crystal was prepared by adopting a high-temperature melt spontaneous crystallization method. The method included the following steps:

[0054] 8.33 g of SrSe, 13.98 g of HgSe and 11.53 g of GeSe.sub.2 were weighed (i.e., SrSe:HgSe:GeSe.sub.2=0.05 mol:0.05 mol:0.05 mol) and were uniformly mixed to obtain a mixture, then the mixture was contained in a Φ12 mm*200 mm quartz glass tube, vacuum pumping to 10.sup.−3Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a tubular growing furnace, temperature was slowly increased to 950° C., the temperature was kept constant for 72 h, slow cooling to room temperature was performed at speed of 1° C./h, and the tubular growing furnace was closed; the quartz glass tube was cut open after cooling to obtain a Φ12 mm*60 mm yellow SrHGeSe.sub.4 crystal.

EXAMPLE 2

[0055] A SrHgGeSe.sub.4 nonlinear optical crystal was prepared by adopting a crucible descending method. The method included the following steps:

[0056] 33.32 g of SrSe, 55.92 g of HgSe and 39.45 g of GeSe.sub.2 were weighed (Sr:Hg:Ge:Se=0.2 mol:0.2 mol:0.2 mol:0.8 mol) and were uniformly mixed to obtain a mixture, then the mixture was contained in a Φ25 mm*200 mm quartz glass tube, vacuum pumping to 10.sup.−3

[0057] Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a crystal growing furnace, temperature was slowly increased to 950° C. to melt the raw materials, and the growing device was vertically descended at speed of 10 mm'h after the raw materials were completely melted; the crystal grew for 5 d, and after growth was completed, the growing device was cooled to room temperature in 50 h to obtain a Φ25 mm*60 mm yellow SrHgGeSe.sub.4 nonlinear optical crystal.

EXAMPLE 3

[0058] A SHgGeSe.sub.4 nonlinear optical crystal was prepared by adopting a high-temperature melt spontaneous crystallization method. The method included the following steps:

[0059] A powdered SrHgGeSe.sub.4 compound was weighed and contained in a Φ10 mm*100 mm quartz glass tube, vacuum pumping to 10.sup.−3 Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a tubular growing furnace, temperature was slowly increased to 1000° C., the temperature was kept constant for 24 h, slow cooling to room temperature was performed at speed of 10° C./h, and the tubular growing furnace was closed; the quartz glass tube was cut open after cooling to obtain a Φ10mm *60 mm yellow SrHgGeSe.sub.4 nonlinear optical crystal.

EXAMPLE 4

[0060] A SrHgGeSe.sub.4 nonlinear optical crystal was prepared by adopting a crucible descending method. The method included the following steps:

[0061] A powdered SrHgGeSe.sub.4 compound was weighed and contained in a Φ20 mm*200 mm quartz glass tube, vacuum pumping to 10.sup.−3 Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a crystal growing furnace, temperature was slowly increased to 1000° C. to melt the raw materials, and the growing device was vertically descended at speed of 0.1 mm/h after the raw materials were completely melted; the crystal grew for 20 d, and after growth was completed, the growing device was cooled to room temperature in 40 h to obtain a Φ20 mm*50 mm yellow SrHgGeSe.sub.4 nonlinear optical crystal.

[0062] After tests, the SrHgGeSe.sub.4 nonlinear optical crystals prepared in examples 1-4 belong to an orthorhombic crystal system, have a space group Ama2, have the following cell parameters: a=10.8345Å, b=10.7441Å, c=6.6392Å, α=β=γ=90°, Z=4, V=772.85Å.sup.3, and have the advantages of great nonlinear optical effect (4.9 times of that of AgGaS.sub.2 under the same conditions), wide light transmitting band (0.5-18 μm), high double refraction, ability of realizing type-I and type-II phase matching, good mechanical properties, breakage resistance, deliquescence resistance, and easiness in cutting, polishing and preserving. FIG. 1 illustrates a structural schematic view of the SrHgGeSe.sub.4 nonlinear optical crystal.

EXAMPLE 5

[0063] A BaHgGeSe.sub.4 crystal was prepared by adopting a high-temperature melt spontaneous crystallization method.

[0064] 10.82 g of BaSe, 13.98 g of HgSe and 11.53 g of GeSe.sub.2 were weighed (i.e., BaSe:HgSe:GeSe.sub.2=0.05 mol:0.05 mol:0.05 mol) and were uniformly mixed to obtain a mixture, then the mixture was contained in a Φ12 mm:200 mm quartz glass tube, vacuum pumping to 10.sup.−3Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a tubular growing furnace, temperature was slowly increased to 900° C. the temperature was kept constant for 72 h, slow cooling to room temperature was performed at speed of 1° C./h, and the tubular growing furnace was closed; the quartz glass tube was cut open after cooling to obtain a Φ12 mm*60 mm yellow BaHgGeSe.sub.4 crystal.

EXAMPLE 6

[0065] A BaHgGeSe.sub.4 crystal was prepared by adopting a crucible descending method.

[0066] 43.26 g of BaSe, 55.92 g of HgSe and 39.45 g of GeSe.sub.2 were weighed (Ba:Hg:Ge:Se=0.2 mol:0.2 mol:0.2 mol:0.8 mol) and were uniformly mixed to obtain a mixture, then the mixture was contained in a Φ25 mm*200 mm quartz glass tube, vacuum pumping to 10.sup.−3Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a crystal growing furnace, temperature was slowly increased to 950° C. to melt the raw materials, and the growing device was vertically descended at speed of 10 mm/h after the raw materials were completely melted; the crystal grew for 5 d, and after growth was completed, the growing device was cooled to room temperature in 50 h to obtain a Φ25 mm*60 mm yellow BaHgGeSe.sub.4 nonlinear optical crystal.

EXAMPLE 7

[0067] A BaHgGeSe.sub.4 crystal was prepared by adopting a high-temperature melt spontaneous crystallization method.

[0068] A powdered BaHgGeSe.sub.4 compound was weighed and contained in a Φ10 mm*100 mm quartz glass tube, vacuum pumping to 10.sup.−3Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a tubular growing furnace, temperature was slowly increased to 1000° C., the temperature was kept constant for 24 h, slow cooling to room temperature was performed at speed of 10° C./h and the tubular growing furnace was closed; the quartz glass tube was cut open after cooling to obtain a Φ10 mm*60 mm yellow BaHgGeSe.sub.4 nonlinear optical crystal.

EXAMPLE 8

[0069] A BaHgGeSe.sub.4 crystal was prepared by adopting a crucible descending method.

[0070] A powdered BaHgGeSe.sub.4 compound was weighed and contained in a Φ20 mm*200 mm quartz glass tube, vacuum pumping to 10.sup.−3Pa was performed, then the quartz glass tube was sealed by adopting oxyhydrogen flame and placed in a crystal growing furnace, temperature was slowly increased to 1000° C. to melt the raw materials, and the growing device was vertically descended at speed of 0.1 mm/h after the raw materials were completely melted; the crystal grew for 20 d, and after growth was completed, the growing device was cooled to room temperature in 40 h to obtain a Φ20 mm*50mm yellow BaHgGeSe.sub.4 nonlinear optical crystal.

[0071] After tests, the BaHgGeSe.sub.4 nonlinear optical crystals prepared in examples 5-8 belong to an orthorhombic crystal system, have a space group Ama2, have the following cell parameters: a=11.255Å, b=11.033Å, c=6.685Å, α=β=γ=90°, Z=4, V=830.12Å.sup.3, have a frequency doubling effect, and have a light transmitting range of 0.55-18 μm. FIG. 2 illustrates a structural schematic view of the BaHgGeSe.sub.4 nonlinear optical crystal.

EXAMPLE 9

[0072] The crystal prepared in each example was used to fabricate a nonlinear optical device. The working principle of the device was as illustrated in FIG. 3, in which 1 represents a laser, 2 represents an incident laser beam, 3 represents a nonlinear optical crystal SrHgGeSe.sub.4 or BaHgGeSe.sub.4 after crystal post-treatment and optical processing, 4 represents a generated emergent laser beam, and 5 represents a filter. The working principle was as follows: the incident laser beam 2 emitted from the laser 1 was enabled to enter the SrHgGeSe.sub.4 monoctystal or the BaHgGeSe.sub.4 monocrystal 3 prepared in each example, and the generated emergent laser beam 4 passed through the filter 5 to obtain a required laser beam.

[0073] The SrHgGeSe.sub.4 crystal prepared in example 1 was used to fabricate the nonlinear optical device. At room temperature, a Q-switched Ho:Tm:Cr:YAG laser was used as a light source, incident light was infrared light with a wavelength of 2090 nm, frequency-doubled light with a wavelength of 1045 nm was output, the laser intensity was 4.9 times of that of AgGaS.sub.2 under the same conditions. When the crystals prepared in examples 2-4 were used to fabricate the nonlinear optical devices, the same results were obtained.

[0074] The BaHgGeSe.sub.4 crystal prepared in example 5 was used to fabricate the nonlinear optical device. At room temperature. a Q-switched Ho:Tm:Cr:YAG laser was used as a light source, incident light was infrared light with a wavelength of 2090 nm, frequency-doubled light with a wavelength of 10445 nm was output, the laser intensity was 2.2 times of that of AgGaS.sub.2 under the same conditions. When the crystals prepared in examples 6-8 were used to fabricate the nonlinear optical devices, the same results were obtained.

[0075] The nonlinear optical device may be a double-frequency generator, a frequency up and down converter, an optical parametric oscillator, an optical parametric amplifier, or the like.

[0076] Apparently, the above examples of the present application are just examples used for clearly describing the present application instead of limitations to the implementation modes of the present application. Those skilled in the art may also make other different changes or variations based on the description. It is impossible to exhaust all implementation modes here. All obvious changes or variations derived from the technical solution of the present application shall also be included in the scope of protection of the present application.