Deep ultraviolet non-linear optical crystal of barium borate hydrate, preparation method therefor and use thereof

Abstract

Provided area deep ultraviolet non-linear optical crystal of barium borate hydrate, a preparation method therefor and the use thereof. The chemical formula of the crystal is Ba.sub.2B.sub.11O.sub.22H.sub.7, belonging to monoclinic system, with the space group thereof being P2.sub.1, the crystal cell parameters thereof being a=6.7719(10) , b=21.1195(4) , c=6.8274(10) , =119.3950(10) , and the molecular weight thereof being 752.65. The non-linear optical crystal of borate is obtained by means of programmed cooling or natural cooling using a hydrothermal method. The crystal powder has a frequency-doubled effect of about 2 times that of KDP (KH.sub.2PO.sub.4) and an ultraviolet cut-off edge of below 175 nm and can be used as a deep ultraviolet non-linear optical crystal. The growth process of the crystal has advantages such as simple, a low cost, a low toxicity, a short growth cycle, stable physical and chemical properties, etc. The deep ultraviolet non-linear optical crystal of barium borate hydrate Ba.sub.2B.sub.11O.sub.22H.sub.7 is widely used in the preparation of non-linear optical devices such as frequency doubling generators, upper frequency converters, lower frequency converters, optical parametric oscillators etc.

Claims

1. A deep ultraviolet non-linear optical crystal of barium borate hydrate, having a formula of Ba.sub.2B.sub.11O.sub.22H.sub.7, belonging to the monoclinic system, having a space group of P2.sub.1,with lattice parameters of a=6.7719(10) , b=21.1195(4) , c=6.8274(10) , =119.3950(10), and a molecular weight of 752.65.

2. A method for preparing the deep ultraviolet non-linear optical crystal of barium borate hydrate according to claim 1, wherein it uses a hydrothermal method and is conducted specifically according to the following steps: (a) BaCl.sub.2, Ba(CH.sub.3COO).sub.2.H.sub.2O, BaSO.sub.4, Ba(ClO.sub.4).sub.2, BaCO.sub.3 or Ba(NO.sub.3).sub.2 is added into the polytetrafluoroethylene liner of a 23-125 mL high-pressure reactor, H.sub.3BO.sub.3 or B.sub.2O.sub.3 is then added, and then 8-70 mL of deionized water is added, followed by mixing uniformly to obtain a mixture solution; In said Step (a), the molar ratio of Ba.sup.2+ to BO.sub.3.sup.3 is 1:0.3-6; the molar ratio of Ba.sup.2+ to B.sub.2O.sub.3 is 1:0.15-3; (b) into the mixture solution of Step (a), a mineralizer lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia or ethylenediamine is added and mixed, wherein the volume ratio of mineralizer and mixture solution is 1:2-70; (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) is tightened, and then the polytetrafluoroethylene liner is loaded into the corresponding high-pressure reactor, followed by tightening the piston of the reactor; (d) The high-pressure reactor of Step (c) is placed in a thermotank, heated to 120-210 C. at a rate of 20-60 C./h, held at this temperature for 3-25 days, and then cooled to room temperature by slow cooling at a rate of 1-50 C./h or natural cooling; (e) The high-pressure reactor is opened and the solution containing the crystal is filtered to obtain a transparent crystal, which is deep ultraviolet non-linear optical crystal of barium borate hydrate Ba.sub.2B.sub.11O.sub.22H.sub.7 as analyzed and identified by X-Ray Single Crystal Diffactometor.

3. The method for preparing the deep ultraviolet non-linear optical crystal of barium borate hydrate according to claim 2, wherein the high-pressure reactor of said Step (c) is a clean and contamination-free high-pressure reactor.

4. The method for preparing the deep ultraviolet non-linear optical crystal of barium borate hydrate according to claim 2, wherein it is conducted by using the hydrothermal method according to the following chemical reaction equations:
2BaCl.sub.2+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4Cl.sup.+11H.sub.2O+4H.sup.+(1)
2Ba(CH.sub.3COO).sub.2.H.sub.2O+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4CH.sub.3COO.sup.+13H.sub.2O+4H.sup.+(2)
2BaSO.sub.4+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2SO.sub.4.sup.2+11H.sub.2O+4H.sup.+(3)
2Ba(ClO.sub.4).sub.2+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4ClO.sub.4.sup.+11H.sub.2O+4H.sup.+(4)
2BaCO.sub.3+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2CO.sub.3.sup.2+11H.sub.2O+4H.sup.+(5)
2Ba(NO.sub.3).sub.2+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4NO.sub.3.sup.+11H.sub.2O+4H.sup.+(6)
2BaCl.sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4Cl.sup.+4H.sup.+(7)
2Ba(CH.sub.3COO).sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4CH.sub.3COO.sup.+4H.sup.+(8)
2BaSO.sub.4+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2SO.sub.4.sup.2+4H.sup.+(9)
2Ba(ClO.sub.4).sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4ClO.sub.4.sup.+4H.sup.+(10)
2BaCO.sub.3+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2CO.sub.3.sup.2+4H.sup.+(11)
2Ba(NO.sub.3).sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4NO.sub.3.sup.+4H.sup.+(12).

5. A use of the deep ultraviolet non-linear optical crystal of barium borate hydrate Ba.sub.2B.sub.11O.sub.22H.sub.7 according to claim 2, wherein the non-linear optical crystal of barium borate hydrate Ba.sub.2B.sub.11O.sub.22H.sub.7 is used for preparing non-linear optical devices, including frequency doubling generator, upper frequency converter, lower frequency converter or optical parametric oscillator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an X-ray diffraction pattern of barium borate hydrate of the present invention;

(2) FIG. 2 is a diagram of the working principle of the non-linear optical device prepared in the present invention, wherein 1 is a laser generator, 2 is a convex lens, 3 is deep ultraviolet non-linear optical crystal of barium borate hydrate Ba.sub.2B.sub.11O.sub.22H.sub.7, 4 is a beam splitter prism and 5 is a filter, and is refracted light frequency, equal to incident light frequency or 2 times as much as incident light frequency.

EXAMPLES

(3) The present invention will be described in details hereinafter in combination of the accompanying drawings and the following examples:

Example 1

(4) The crystal was prepared according to
2BaCl.sub.2+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4Cl.sup.+11H.sub.2O+4H.sup.+
and the specific procedure as follows:

(5) (a) According to a molar ratio of BaCl.sub.2:H.sub.3BO.sub.3=1:4, BaCl.sub.2 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor. H.sub.3BO.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(6) (b) Into the mixture solution of Step (a), a mineralizer 1 mL of 3 mol/L LiOH solution was added and mixed, wherein the volume ratio of the mineralizer to the mixture solution was 1:10;

(7) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(8) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 180 C. at a rate of 20 C./h, held at this temperature for 3 days, followed by slowly cooling to room temperature at a rate of 2 C./h;

(9) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered repeatedly to obtain a relatively transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 2

(10) The crystal was prepared according to
2Ba(CH.sub.3COO).sub.2.H.sub.2O+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4CH.sub.3COO.sup.+13H.sub.2O+4H.sup.+
and the specific procedure as follows:

(11) (a) According to a molar ratio of Ba(CH.sub.3COO).sub.2.H.sub.2O:H.sub.3BO.sub.3=1:2, Ba(CH.sub.3COO).sub.2.H.sub.2O was added into the polytetrafluoroethylene liner of a 80 mL high-pressure reactor, H.sub.3BO.sub.3 was then added, and then 35 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(12) (b) Into the mixture solution of Step (a), a mineralizer 0.5 mL of 3 mol/L NaOH solution was added and mixed, wherein the volume ratio of the mineralizer to the mixture solution was 1:70;

(13) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(14) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 200 C. at a rate of 30 C./h, held at this temperature for 6 days, followed by naturally cooling to room temperature;

(15) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered repeatedly to obtain a relatively transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 3

(16) The crystal was prepared according to
2BaSO.sub.4+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2SO.sub.4.sup.2+11H.sub.2O+4H.sup.+
and the specific procedure as follows:

(17) (a) According to a molar ratio of BaSO.sub.4:H.sub.3BO.sub.3=1:6, BaSO.sub.4 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, H.sub.3BO.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(18) (b) Into the mixture solution of Step (a), a mineralizer 0.5 mL of 3 mol/L KOH solution was added and mixed, wherein the volume ratio of the mineralizer to the mixture solution was 1:20;

(19) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the high-pressure reactor;

(20) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 210 C. at a rate of 50 C./h, held at this temperature for 10 days, followed by slowly cooling to room temperature at a rate of 30 C./h;

(21) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor,

Example 4

(22) The crystal was prepared according to
2Ba(ClO.sub.4).sub.2+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4ClO.sub.4.sup.+11H.sub.2O+4H.sup.+
and the specific procedure as follows:

(23) (a) According to a molar ratio of Ba(ClO.sub.4).sub.2:H.sub.3BO.sub.3=1:5, Ba(ClO.sub.4).sub.2 was added into the polytetrafluoroethylene liner of a 125 mL high-pressure reactor, H.sub.3BO.sub.3 was then added, and then 70 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(24) (b) Into the mixture solution of Step (a), a mineralizer 5 mL of ethylenediamine was added and mixed, wherein the volume ratio of the mineralizer to the mixture solution was 1:14;

(25) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(26) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 120 C. at a rate of 25 C./h, held at this temperature for 25 days, followed by naturally cooling to room temperature;

(27) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 5

(28) The crystal was prepared according to
2BaCO.sub.3+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2CO.sub.3.sup.2+11H.sub.2O+4H.sup.+
and the specific procedure as follows:

(29) (a) According to a molar ratio of BaCO.sub.3:H.sub.3BO.sub.3=1:6, BaCO.sub.3 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, H.sub.3BO.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(30) (b) Into the mixture solution of Step (a), a mineralizer 5 mL of ammonia was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:2;

(31) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(32) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 210 C. at a rate of 40 C./h, held at this temperature for 6 days, followed by slowly cooling to room temperature at a rate of 25 C./h;

(33) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 6

(34) The crystal was prepared according to
2Ba(NO.sub.3).sub.2+11H.sub.3BO.sub.3.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4NO.sub.3.sup.+11H.sub.2O+4H.sup.+
and the specific procedure as follows:

(35) (a) According to a molar ratio of Ba(NO.sub.3).sub.2:H.sub.3BO.sub.3=1:0.3, Ba(NO.sub.3).sub.2 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, H.sub.3BO.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(36) (b) Into the mixture solution of Step (a), a mineralizer 0.5 mL of KOH was added and mixed, wherein the volume ratio of the mineralizer to the mixture solution was 1:20;

(37) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(38) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 210 C. at a rate of 40 C./h, held at this temperature for 6 days, followed by slowly cooling to room temperature at a rate of 25 C./h;

(39) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 7

(40) The crystal was prepared according to
2BaCl.sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4Cl.sup.+4H.sup.+
and the specific procedure as follows:

(41) (a) According to a molar ratio of BaCl.sub.2:B.sub.2O.sub.3=1:2, BaCl.sub.2 was added was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, B.sub.2O.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(42) (b) Into the mixture solution of Step (a), a mineralizer 1 mL of 3 mol/L LiOH solution was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:10;

(43) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(44) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 180 C. at a rate of 20 C./h, increased, held at this temperature for 3 days, followed by slowly cooling to room temperature at a rate of 2 C./h;

(45) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered repeatedly to obtain a relatively transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 8

(46) The crystal was prepared according to
2Ba(CH.sub.3COO).sub.2.H.sub.2O+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4CH.sub.3COO.sup.+4H.sup.+
and the specific procedure as follows:

(47) (a) According to a molar ratio of Ba(CH.sub.3COO).sub.2.H.sub.2O:B.sub.2O.sub.3=1:1, Ba(CH.sub.3COO).sub.2.H.sub.2O was added into the polytetrafluoroethylene liner of a 80 mL high-pressure reactor, B.sub.2O.sub.3 was then added, and then 35 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(48) (b) Into the mixture solution of Step (a), a mineralizer 0.5 mL of 3 mol/L NaOH solution was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:70;

(49) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(50) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 200 C. at a rate of 30 C./h, held at this temperature for 6 days, followed by naturally cooling to room temperature;

(51) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered repeatedly to obtain a relatively transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 9

(52) The crystal was prepared according to
2BaSO.sub.4+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2SO.sub.4.sup.2+4H.sup.+
and the specific procedure as follows:

(53) (a) According to a molar ratio of BaSO.sub.4:B.sub.2O.sub.3=1.3. BaSO.sub.4 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, B.sub.2O.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(54) (b) Into the mixture solution of Step (a), a mineralizer 0.5 mL of 3 mol/L KOH solution was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:20;

(55) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(56) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 210 C. at a rate of 50 C./h, held at this temperature for 10 days, followed by slowly cooling to room temperature at a rate of 30 C./h;

(57) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 10

(58) The crystal was prepared according to
2Ba(ClO.sub.4).sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4ClO.sub.4.sup.+4H.sup.+
and the specific procedure as follows:

(59) (a) According to a molar ratio of Ba(ClO.sub.4).sub.2:B.sub.2O.sub.3=1:2.5, Ba(ClO.sub.4).sub.2 was added into the polytetrafluoroethylene liner of a 125 mL high-pressure reactor, B.sub.2O.sub.3 was then added, and then 70 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(60) (b) Into the mixture solution of Step (a), a mineralizer 5 mL of ethylenediamine was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:14;

(61) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(62) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 120 C. at a rate of 25 C./h, held at this temperature for 25 days, followed by naturally cooling to room temperature;

(63) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 11

(64) The crystal was prepared according to
2BaCO.sub.3+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+2CO.sub.3.sup.2+4H.sup.+
and the specific procedure as follows:

(65) (a) According to a molar ratio of BaCO.sub.3:B.sub.2O.sub.3=1:3, BaCO.sub.3 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, B.sub.2O.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(66) (b) Into the mixture solution of Step (a), a mineralizer 5 mL of ammonia was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:2;

(67) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(68) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 210 C. at a rate of 40 C./h, increased, held at this temperature for 6 days, followed by slowly cooling to room temperature at a rate of 25 C./h;

(69) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 12

(70) The crystal was prepared according to
2Ba(NO.sub.3).sub.2+11/2B.sub.2O.sub.3+11/2H.sub.2O.fwdarw.Ba.sub.2B.sub.11O.sub.22H.sub.7+4NO.sub.3.sup.+4H.sup.+
and the specific procedure as follows:

(71) (a) According to a molar ratio of Ba(NO.sub.3).sub.2:B.sub.2O.sub.3=1:0.15, Ba(NO.sub.3).sub.2 was added into the polytetrafluoroethylene liner of a 23 mL high-pressure reactor, B.sub.2O.sub.3 was then added, and then 10 mL of deionized water was added, followed by mixing uniformly to obtain a mixture solution;

(72) (b) Into the mixture solution of Step (a), a mineralizer 0.5 mL of KOH was added and mixed, wherein the volume ratio of the mineralizer and the mixture solution was 1:20;

(73) (c) The lid of the polytetrafluoroethylene liner charged with the mixture solution of Step (b) was tightened, and then the polytetrafluoroethylene liner was loaded into the corresponding clean and contamination-free high-pressure reactor, followed by tightening the piston of the reactor;

(74) (d) The high-pressure reactor of Step (c) was placed in a thermotank, heated to 210 C. at a rate of 40 C./h, held at this temperature for 6 days, followed by slowly cooling to room temperature at a rate of 25 C./h;

(75) (e) The high-pressure reactor was opened and the solution containing the crystal was filtered to obtain a transparent Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal as analyzed and identified by X-Ray Single Crystal Diffactometor.

Example 13

(76) Any one of the non-linear optical crystals obtained in Examples 1-12 was arranged at the position (3) as shown in FIG. 2. At room temperature, when a Q-switched Nd:YAG laser generator with a setting of 1,064 nm was used as light source, it was observed that clear frequency-doubled green light at 532 nm was output, the output intensity of which was twice of that of KDP under the same conditions;

(77) As shown in FIG. 2, Q-switched Nd:YAG laser generator 1 emitted an infrared light at a wavelength of 1,064 nm, which then entered the Ba.sub.2B.sub.11O.sub.22H.sub.7 non-linear optical crystal after passing through the convex lens 2, and then a frequency-doubled green light at a wavelength of 532 nm was generated. The output light beam 4 comprised both the infrared light at a wavelength of 1,064 nm and the green light at wavelength of 532 nm. After filtration by filter 5, the frequency-doubled light at a wavelength of 532 nm was obtained.