NONLINEAR OPTICAL CRYSTAL OF GUANIDINIUM TETRAFLUOROBORATE, PREPARATION METHOD AND USE THEREOF

Abstract

A nonlinear optical crystal of guanidinium tetrafluoroborate has a chemical formula of [C(NH.sub.2).sub.3]BF.sub.4 and a molecular weight of 146.89, belongs to the trigonal crystal system, has a space group of R3m; has lattice parameters of a=7.4634(10)Å, b=7.4634(10)Å, c=9.1216(19) (6)Å, and Z=3; has an ultraviolet cutoff edge of 200 nm; and has a frequency-multiplication response that is 4-5 times that of the commercialized nonlinear optical crystal KDP. A hydrothermal method, a room-temperature solution method, an evaporation method or a solvothermal method is used to grow the crystal in a centimeter-scaled size. The crystal can produce frequency-doubling, frequency-tripling, frequency-quadrupling, frequency-quintupling or frequency-sextupling harmonic light output from the fundamental frequency light of 1064 nm generated by a Nd:YAG laser, and/or can produce ultraviolet and deep-ultraviolet frequency-multiplication light output below 200 nm.

Claims

1. A nonlinear optical crystal of guanidinium tetrafluoroborate, wherein the crystal has a chemical formula of [C(NH.sub.2).sub.3]BF.sub.4 and a molecular weight of 146.89; the crystal belongs to the trigonal crystal system; the crystal's space group is R3m; the crystal's lattice parameters are a=7.4634(10)Å, b=7.4634(10)Å, c=9.1216(19) (6)Å, Z=3; and the crystal's ultraviolet cut-off edge is below 200 nm.

2. A method for preparing the nonlinear optical crystal of guanidinium tetrafluoroborate according to claim 1, wherein a hydrothermal method, a room temperature solution method, an evaporation method or a solvothermal method is utilized to prepare the crystal; wherein the hydrothermal method for preparing the nonlinear optical crystal of guanidinium tetrafluoroborate comprises: a. mixing a NH.sub.2 group-containing compound and a BF.sub.4 group-containing compound in a molar ratio of NH.sub.2:BF.sub.4=3:1, and fully grinding the compounds, then adding 10-50 mL of deionized water to mix and dissolve the compounds thoroughly and form a mixture solution; wherein the NH.sub.2 group-containing compound is one or more of guanidinium carbonate, guanidinium sulfate, guanidinium nitrate and guanidinium phosphate, and the BF.sub.4 group-containing compound is one or more of tetrafluoroboric acid, ammonium tetrafluoroborate, lithium tetrafluoroborate and sodium tetrafluoroborate; b. transferring the mixture solution of the step a into a polytetrafluoroethylene lining of an autoclave reactor with a volume of 25-100 mL, and sealing the autoclave reactor tightly; c. placing the autoclave reactor of step b in an incubator, and heating up the incubator to 50-230° C. at a rate of 20-60° C./hour, keeping the incubator at the temperature constantly for 3-15 days, and then reducing the temperature to room temperature at a cooling rate of 10-100° C./day; and d. opening the autoclave reactor, and obtaining a centimeter-scale large-size nonlinear optical crystal of guanidinium tetrafluoroborate in a colorless clear solution; the room temperature solution method for preparing the nonlinear optical crystal of guanidinium tetrafluoroborate comprises: a. mixing a NH.sub.2 group-containing compound and a BF.sub.4 group-containing compound in a molar ratio of NH.sub.2:BF.sub.4=3:1, fully grinding the compounds, then adding 10-200 mL deionized water to mix and dissolve the compounds thoroughly to obtain a mixture solution; wherein the NH.sub.2 group-containing compound is one or more of guanidinium carbonate, guanidinium sulfate, guanidinium nitrate and guanidinium phosphate, and the BF.sub.4 group-containing compound is one or more of tetrafluoroboric acid, ammonium tetrafluoroborate, lithium tetrafluoroborate and sodium tetrafluoroborate; b. transferring the mixture solution of step a into a beaker with a volume of 50-300 mL, conducting an ultrasonic treatment to make the mixture solution fully mixed and dissolved, adjusting pH value of the solution to 1-11, filtering the solution through qualitative filter paper, and then sealing the beaker with polyvinyl chloride film, placing the sealed beaker in a static environment with no shaking, no pollution, and no air convection, poking a number of small holes on the seal to adjust the volatilization rate of the solvent in the solution, and keeping the beaker at room temperature until the growth ends, then obtaining nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 1-20 mm.sup.3; the evaporation method for preparing the nonlinear optical crystal of guanidinium tetrafluoroborate comprises: a. mixing a NH.sub.2 group-containing compound and a BF.sub.4 group-containing compound in a molar ratio of NH.sub.2:BF.sub.4=3:1, fully grinding the compounds, then adding 10-200 mL deionized water to mix and dissolve the compounds thoroughly to form a mixture solution; wherein the NH.sub.2 group-containing compound is one or more of guanidinium carbonate, guanidinium sulfate, guanidinium nitrate and guanidinium phosphate, and the BF.sub.4 group-containing compound is one or more of tetrafluoroboric acid, ammonium tetrafluoroborate, lithium tetrafluoroborate and sodium tetrafluoroborate; b. transferring the mixture solution of step a into a beaker with a volume of 50-300 mL, conducting an ultrasonic treatment to make the mixture solution fully mixed and dissolved, and filtering the solution through qualitative filter paper; c. placing the beaker of step b in an incubator, and heating up the incubator to 50-120° C. at a rate of 5-10° C./h, keeping the beaker at the temperature constantly for 3-15 days until the growth ends, then obtaining nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 1-20 mm.sup.3; and the solvothermal method for preparing the nonlinear optical crystal of guanidinium tetrafluoroborate comprises: a. mixing a NH.sub.2 group-containing compound and a BF.sub.4 group-containing compound in a molar ratio of NH.sub.2:BF.sub.4=3:1, fully grinding the compounds, then adding 10-200 mL solvent to mix and dissolve the compounds thoroughly to form a mixture solution; wherein the NH.sub.2 group-containing compound is one or more of guanidinium carbonate, guanidinium sulfate, guanidinium nitrate and guanidinium phosphate; the BF.sub.4 group-containing compound is one or more of tetrafluoroboric acid, ammonium tetrafluoroborate, lithium tetrafluoroborate and sodium tetrafluoroborate; and the solvent is deionized water, absolute ethanol, hydrofluoric acid or tetrafluoroboric acid; b. transferring the mixture solution of step a into a beaker with a volume of 50-300 mL, conducting an ultrasonic treatment to make the mixture solution fully mixed and dissolved, adjusting pH value of the solution to 1-11, filtering the solution through qualitative filter paper, and then sealing the beaker with polyvinyl chloride film, placing the sealed beaker in a static environment with no shaking, no pollution, and no air convection, poking a number of small holes on the seal to adjust the volatilization rate of the solvent in the solution, and keeping the beaker at room temperature until the growth ends, then obtaining nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 1-20 mm.sup.3.

3. A device selected from the group consisting of multi-band frequency-multiplication devices or optical elements, wherein the device includes the nonlinear optical crystal of guanidinium tetrafluoroborate according to claim 1.

4. A method of producing frequency-doubling, frequency-tripling, frequency-quadrupling, frequency-quintupling or frequency-sextupling harmonic light output comprising applying fundamental frequency light of 1064 nm generated by a Nd:YAG laser to the nonlinear optical crystal of guanidinium tetrafluoroborate according to claim 1.

5. The nonlinear optical crystal of guanidinium tetrafluoroborate according to claim 1, wherein the crystal is capable of producing a deep ultraviolet frequency-multiplication light output below 200 nm.

6. The device according to claim 3, wherein the device is a frequency-multiplication generator, a frequency up or down converter, or an optical parametric oscillator.

Description

DESCRIPTION OF DRAWINGS

[0036] FIG. 1 is the XRD spectrum of the present invention, and the spectrum is consistent with the theoretical XRD spectrum, which proves the existence of the compound guanidinium tetrafluoroborate;

[0037] FIG. 2 is the photogram of nonlinear optical crystal of guanidinium tetrafluoroborate of the present invention;

[0038] FIG. 3 is the functional diagram of a nonlinear optical device made of a nonlinear optical crystal of guanidinium tetrafluoroborate according to the present invention, wherein 1 represents a laser, 2 represents an emission light beam, 3 represents the nonlinear optical crystal of guanidinium tetrafluoroborate, and 4 represents an emergent light beam, and 5 represents a filter.

SPECIFIC MODES FOR CARRYING OUT THE INVENTION

Example 1

[0039] Said hydrothermal method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0040] a. Guanidinium carbonate and tetrafluoroboric acid were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0041] b. The mixture solution of step a was transferred into the polytetrafluoroethylene lining of an autoclave reactor with a volume of 25 mL, then the reactor was sealed tightly; [0042] c. The autoclave reactor of step b was placed in an incubator; the incubator was heated up to 50° C. at a rate of 20° C./h and kept at this temperature constantly for 3 days, then the temperature was reduced to room temperature at a cooling rate of 10° C./day; [0043] d. The autoclave reactor was opened, and nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 11×10×12 mm.sup.3 was obtained in a colorless clear solution.

Example 2

[0044] Said hydrothermal method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0045] a. Guanidinium sulfate and lithium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 50 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0046] b. The mixture solution of step a was transferred into the polytetrafluoroethylene lining of an autoclave reactor with a volume of 100 mL, then the reactor was sealed tightly; [0047] c. The autoclave reactor of step b was placed in an incubator; the incubator was heated up to 230° C. at a rate of 60° C./h and kept at this temperature constantly for 15 days, then the temperature was reduced to room temperature at a cooling rate of 100° C./day; [0048] d. The autoclave reactor was opened, and nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 18×20×33 mm.sup.3 was obtained in a colorless clear solution.

Example 3

[0049] Said hydrothermal method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0050] a. Guanidinium nitrate and ammonium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 40 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0051] b. The mixture solution of step a was transferred into the polytetrafluoroethylene lining of an autoclave reactor with a volume of 70 mL, then the reactor was sealed tightly; [0052] c. The autoclave reactor of step b was placed in an incubator; the incubator was heated up to 150° C. at a rate of 40° C./h and kept at this temperature constantly for 7 days, then the temperature was reduced to room temperature at a cooling rate of 60° C./day; [0053] d. The autoclave reactor was opened, and nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 11×22×23 mm.sup.3 was obtained in a colorless clear solution.

Example 4

[0054] Said hydrothermal method was used to prepare nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0055] a. Guanidinium phosphate and sodium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10-50 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0056] b. The mixture solution of step a was transferred into the polytetrafluoroethylene lining of an autoclave reactor with a volume of 50 mL, then the reactor was sealed tightly; [0057] c. The autoclave reactor of step b was placed in an incubator; the incubator was heated up to 200° C. at a rate of 50° C./h and kept at this temperature constantly for 7 days, then the temperature was reduced to room temperature at a cooling rate of 80° C./day; [0058] d. The autoclave reactor was opened, and nonlinear optical crystal of guanidinium tetrafluoroborate in a centimeter-scaled large-size of 10×21×22 mm.sup.3 was obtained in a colorless clear solution.

Example 5

[0059] Said room temperature solution method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0060] a. Guanidinium phosphate and sodium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0061] b. The mixture solution of step a was transferred into a beaker with a volume of 50 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 1; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 1 mm.sup.3 was obtained.

Example 6

[0062] Said room temperature solution method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0063] a. Guanidinium sulfate and lithium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 200 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0064] b. The mixture solution of step a was transferred into a beaker with a volume of 300 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 11; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 20 mm.sup.3 was obtained.

Example 7

[0065] Said room temperature solution method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0066] a. Guanidinium nitrate and lithium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 100 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0067] b. The mixture solution of step a was transferred into a beaker with a volume of 200 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 5; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 12 mm.sup.3 was obtained.

Example 8

[0068] Said room temperature solution method was used to prepare nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0069] a. Guanidinium carbonate and sodium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10-200 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0070] b. The mixture solution of step a was transferred into a beaker with a volume of 150 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 10; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 15 mm.sup.3 was obtained.

Example 9

[0071] Said evaporation method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0072] a. Guanidinium nitrate and tetrafluoroboric acid were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0073] b. The mixture solution of step a was transferred into a beaker with a volume of 50 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; the solution was filtered through qualitative filter paper; c. The beaker of step b was placed in an incubator; the incubator was heated up to 50° C. at a rate of 5° C./h and then kept at this temperature constantly for 3 days; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 1 mm.sup.3 was obtained.

Example 10

[0074] Said evaporation method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0075] a. Guanidinium sulfate and ammonium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 200 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0076] b. The mixture solution of step a was transferred into a beaker with a volume of 300 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; the solution was filtered through qualitative filter paper; [0077] c. The beaker of step b was placed in an incubator; the incubator was heated up to 120° C. at a rate of 10° C./h and then kept at this temperature constantly for 15 days; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 20 mm.sup.3 was obtained.

Example 11

[0078] Said evaporation method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0079] a. Guanidinium carbonate and sodium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 120 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0080] b. The mixture solution of step a was transferred into a beaker with a volume of 250 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; the solution was filtered through qualitative filter paper; [0081] c. The beaker of step b was placed in an incubator; the incubator was heated up to 100° C. at a rate of 10° C./h and then kept at this temperature constantly for 13 days; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 14 mm.sup.3 was obtained.

Example 12

[0082] Said evaporation method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0083] a. Guanidinium phosphate and lithium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10-200 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0084] b. The mixture solution of step a was transferred into a beaker with a volume of 180 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; the solution was filtered through qualitative filter paper; [0085] c. The beaker of step b was placed in an incubator; the incubator was heated up to 100° C. at a rate of 8° C./h and then kept at this temperature constantly for 12 days; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 12 mm.sup.3 was obtained.

Example 13

[0086] Said solvothermal method was used to grow nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0087] a. Guanidinium sulfate and lithium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10 mL of deionized water was added to mix and dissolve the mixture thoroughly; [0088] b. The mixture solution of step a was transferred into a beaker with a volume of 50 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 1; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 10 mm.sup.3 was obtained.

Example 14

[0089] Said solvothermal method was used to prepare nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0090] a. Guanidinium carbonate and sodium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 50 mL of absolute ethanol was added to mix and dissolve the mixture thoroughly; [0091] b. The mixture solution of step a was transferred into a beaker with a volume of 200 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 11; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 1 mm.sup.3 was obtained.

Example 15

[0092] Said solvothermal method was used to prepare nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0093] a. Guanidinium sulfate and ammonium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10 mL of hydrofluoric acid was added to mix and dissolve the mixture thoroughly; [0094] b. The mixture solution of step a was transferred into a beaker with a volume of 300 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 7; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 20 mm.sup.3 was obtained.

Example 16

[0095] Said solvothermal method was used to prepare nonlinear optical crystal of guanidinium tetrafluoroborate, and the specific operation was carried out according to the following steps: [0096] a. Guanidinium carbonate and lithium tetrafluoroborate were fully mixed and grinded in a molar ratio of NH.sub.2:BF.sub.4=3:1, then 10 mL of tetrafluoroboric acid was added to mix and dissolve the mixture thoroughly; [0097] b. The mixture solution of step a was transferred into a beaker with a volume of 170 mL; an ultrasonic treatment was conducted to make it fully mixed and dissolved; pH value of the solution was adjusted to 10; the solution was filtered through qualitative filter paper, sealed with polyvinyl chloride film and placed in a static environment with no shaking, no pollution, and no air convection; a number of small holes were poked on the seal to adjust the volatilization rate of the solvent in the solution; then the solution was kept at room temperature; when the growth ended, nonlinear optical crystal of guanidinium tetrafluoroborate in a size of 13 mm.sup.3 was obtained.

Example 17

[0098] Any nonlinear optical crystal of guanidinium tetrafluoroborate [C(NH.sub.2).sub.3]BF.sub.4 (FIG. 2) obtained in Examples 1-16 was processed in the matching direction, and placed at the position 3 as shown in FIG. 3. At room temperature, a Q-switched Nd: YAG laser was used as the light source; and the incident wavelength was 1064 nm. An infrared light beam 2 with a wavelength of 1064 nm was emitted from the Q-switched Nd: YAG laser 1 and entered the C(NH.sub.2).sub.3]BF.sub.4 monocrystal 3 to generate a green frequency-multiplication light with a wavelength of 532 nm. And its output intensity was about 4.3 times of that of KDP under the same conditions.

Example 18

[0099] Any nonlinear optical crystal of guanidinium tetrafluoroborate [C(NH.sub.2).sub.3]BF.sub.4 (FIG. 2) obtained in Examples 1-16 was processed in the matching direction, and placed at the position 3 as shown in FIG. 3. At room temperature, a Q-switched Nd: YAG laser was used as the light source; and the incident wavelength was 532 nm. An infrared light beam 2 with a wavelength of 532 nm was emitted from the Q-switched Nd: YAG laser 1 and entered the [C(NH.sub.2).sub.3]BF.sub.4 monocrystal 3 to generate a frequency-multiplication light with a wavelength of 266 nm. And its output intensity was about 1.2 times of that of BBO under the same conditions.