U.S. patent application number 15/408438 was filed with the patent office on 2017-10-26 for nonlinear optical crystal and manufacturing method thereof.
The applicant listed for this patent is National Central University. Invention is credited to Bor-Chen CHANG, Wen-Jung CHANG, Tzu-Ling CHAO, Kwang-Hwa LII.
Application Number | 20170307959 15/408438 |
Document ID | / |
Family ID | 59687835 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170307959 |
Kind Code |
A1 |
LII; Kwang-Hwa ; et
al. |
October 26, 2017 |
NONLINEAR OPTICAL CRYSTAL AND MANUFACTURING METHOD THEREOF
Abstract
A nonlinear optical crystal has a chemical formula
Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, wherein X=K or Rb. The
nonlinear optical crystal belongs to tetragonal system With space
group P4nc and Z=2. The unit cell parameters of
Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 are a=b=11.3336(5) .ANG.,
c=5.0017(2) .ANG.; and the unit cell parameters of
Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12 are a=b=11.5038(6) .ANG.. The
two crystals are thermally stable and show strong second harmonic
generation with high laser damage threshold.
Inventors: |
LII; Kwang-Hwa; (Taoyuan
City, TW) ; CHANG; Wen-Jung; (Taoyuan City, TW)
; CHANG; Bor-Chen; (Taipei City, TW) ; CHAO;
Tzu-Ling; (Taichung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National Central University |
Taoyuan City |
|
TW |
|
|
Family ID: |
59687835 |
Appl. No.: |
15/408438 |
Filed: |
January 18, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/3551 20130101;
C01P 2002/72 20130101; C01P 2002/76 20130101; C01P 2002/77
20130101; C01B 33/32 20130101 |
International
Class: |
G02F 1/355 20060101
G02F001/355; C01B 33/32 20060101 C01B033/32 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2016 |
TW |
105112844 |
Claims
1. A nonlinear optical crystal of a formula
Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, wherein X=K or Rb.
2. A nonlinear optical crystal of a formula
Li.sub.2K.sub.4TiOSi.sub.4O.sub.12, wherein the nonlinear optical
crystal belongs to tetragonal system, space group thereof is P4nc,
Z=2 and unit cell parameters are a=b=11.3336(5) .ANG., c=5.0017(2)
.ANG..
3. A nonlinear optical crystal of a formula
Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12, wherein the nonlinear optical
crystal belongs to tetragonal system, space group thereof is P4nc,
Z=2 and unit cell parameters are a=b=11.5038(6) .ANG., c=5.1435(3)
.ANG..
4. A method of manufacturing a nonlinear optical crystal,
comprising: mixing LiF, XF, TiO.sub.2 and SiO.sub.2 to form a first
starting reagent, wherein X=K or Rb; heating the first starting
reagent to a first temperature to melt the first starting reagent
and undergo a reaction; and cooling down the first starting reagent
from the first temperature to a second temperature to crystallize a
nonlinear optical material represented by a formula
Li.sub.2X.sub.4TiOSi.sub.4O.sub.12.
5. The method for manufacturing the nonlinear optical crystal
according to claim 4, wherein a molar ratio of Li:K:Ti:Si in the
first starting reagent is a:b:1:1-4, wherein a and b are between
10-30.
6. The method for manufacturing the nonlinear optical crystal
according to claim 4, wherein a molar ratio of Li:Rb:Ti:Si in the
first starting reagent is c:d:1:1-4, wherein c and d are between
10-30.
7. The method for manufacturing the nonlinear optical crystal
according to claim 4, wherein the first temperature is between
650.degree. C. and 900.degree. C., and the second temperature is
between 550.degree. C. and 700.degree. C.
8. A method of manufacturing a nonlinear optical crystal,
comprising: mixing LiOH.H.sub.2O, KOH, TiO.sub.2, SiO.sub.2 and
H.sub.2O to form a second starting reagent; heating the second
starting reagent to a third temperature to undergo a hydrothermal
reaction at the third temperature to form a supersaturated solution
comprising Li.sub.2K.sub.4TiOSi.sub.4O.sub.12; and cooling down the
second starting reagent from the third temperature to a fourth
temperature to crystallize a nonlinear optical material represented
by a formula Li.sub.2K.sub.4TiOSi.sub.4O.sub.12.
9. The method for manufacturing the nonlinear optical crystal
according to claim 8, wherein a molar ratio of
LiOH.H.sub.2O:KOH:TiO.sub.2:SiO.sub.2 :H.sub.2O in the second
starting reagent is 2:10:1:4:10.
10. The method for manufacturing the nonlinear optical crystal
according to claim 8, wherein the third temperature is between
450.degree. C. and 550.degree. C. and the fourth temperature is
between 300 and 350.degree. C.
Description
RELATED APPLICATIONS
[0001] This application claims priority to Taiwan Application
Serial Number 105112844, filed on Apr. 25, 2016, which is herein
incorporated by reference,
BACKGROUND
[0002] Generally speaking, when light passes through a medium,
optical phenomena such as incidence, reflection or refraction
occur. However, the intensity of laser beam is extremely high and
is coherent, and the nonlinear response relevant to the
polarization of a material will induce an electric field to light
waves when laser wave passes through the material. It might
generate harmonic waves from incident light waves at the sum
frequency and beat frequency. The effect which is different from
linear optical phenomena is called nonlinear optical effects. The
crystals having nonlinear optical properties are called nonlinear
optical crystals.
[0003] One of the most basic and important nonlinear optical effect
is the change of the frequency of light. Nonlinear optical crystals
can be used to change a fixed frequency of a laser to different
frequencies by processes of double frequency, sum frequency, beat
frequency or optical parametric amplification. The second harmonic
generation generated by doubling frequency of nonlinear optical
effects has widespread applications in the application of
laser.
[0004] Nonlinear optical crystals have very important applications
in laser technology. Nonlinear optical crystals can be applied to
scientific research, high power lasers, laser medical cosmetology
and national defense technology. Only a few nonlinear optical
crystals have been successfully commercialized, and thus there is
still a need for new nonlinear optical crystals for various
applications.
CONTENTS OF THE INVENTION
[0005] In accordance with embodiments of the present invention, a
nonlinear optical crystal of the formula
Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, is provided, wherein X=K or
Rb.
[0006] In accordance with embodiments of the present invention, a
nonlinear optical crystal of the formula
Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 is provided, wherein the
nonlinear optical crystal belongs to tetragonal system, space group
thereof is P4nc, Z=2 and the unit cell parameters are
a=b=11.3336(5) .ANG., c=5.0017(2) .ANG..
[0007] In accordance with embodiments of the present invention, a
nonlinear optical crystal of the formula
Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12 is provided, wherein the
nonlinear optical crystal belongs to tetragonal system, space group
thereof is P4nc, Z=2 and the unit cell parameters are
a=b=11.5038(6) .ANG., c=5.1435(3) .ANG..
[0008] In accordance with embodiments of the present invention, a
flux growth method of manufacturing a nonlinear optical crystal
including mixing LiF, XF, TiO.sub.2 and SiO.sub.2 to form a first
starting reagent; heating the first starting reagent to a first
temperature t melt the first starting reagent and to undergo a
reaction; and cooling down the first starting reagent from the
first temperature to a second temperature to crystallize a
nonlinear optical crystal represented by the formula
Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, wherein X=K or Rb.
[0009] In some embodiments, the molar ratio of Li:K:Ti:Si in the
first starting reagent is equal to a:b:1:1.about.4, wherein a and b
are between 10-30.
[0010] In some embodiments, the molar ratio of Li:Rb:Ti:Si in the
first starting reagent is equal to a:b:1:1.about.4, wherein a and b
are between 10-30.
[0011] In some embodiments, the first temperature is between
650.degree. C. and 900.degree. C., and the second temperature is
between 550.degree. C. and 700.degree. C.
[0012] In accordance with embodiments of the present invention, a
method of manufacturing a nonlinear optical crystal is provided,
including mixing LiOH.H.sub.2O, KOH, TiO.sub.2, SiO.sub.2 and
H.sub.2O to form a second starting reagent; heating the second
starting reagent to a third temperature to undergo a
high-temperature, high-pressure hydrothermal reaction at the third
temperature to form a supersaturated solution comprising
Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 ; and cooling down the second
starting reagent from the third temperature to a fourth temperature
to crystallize a nonlinear optical crystal represented by the
formula Li.sub.2K.sub.4TiOSi.sub.4O.sub.12.
[0013] In some embodiments, the molar ratio of
LiOH.H.sub.2O:KOH:TiO.sub.2:SiO.sub.2:H.sub.2O in the second
starting reagent is equal to 2:10:1:4:10.
[0014] In some embodiments, the third temperature is between
450.degree. C. and 550.degree. C., and the fourth temperature is
between 300.degree. C. and 350.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0016] FIG. 1 illustrates an ORTEP drawing of a nonlinear optical
crystal structure, in accordance with some embodiments of the
present invention.
[0017] FIG. 2A illustrates the top view of an ah plane of the
nonlinear optical crystal structure, in accordance with some
embodiments of the present invention.
[0018] FIG. 2B illustrates the connectivity between TiO.sub.5 and
silicate chain in the crystal structure of the nonlinear optical
crystal material, in accordance with some embodiments of the
present invention.
[0019] FIG. 2C illustrates the top view of an ac plane of the
nonlinear optical crystal structure, in accordance with some
embodiments of the present invention.
[0020] FIG. 3A is a powder X-ray diffraction pattern of the
nonlinear optical crystal Li.sub.2K.sub.4TiOSi.sub.4O.sub.12, in
accordance with some embodiments of the present invention.
[0021] FIG. 3B is a powder X-ray diffraction pattern of the
nonlinear optical crystal Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12, in
accordance with some embodiments of the present invention.
[0022] FIG. 4A is the second harmonic generation spectra of the
nonlinear optical crystal Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 and
KH.sub.2PO.sub.4 (KDP), in accordance with sonic embodiments of the
present invention.
[0023] FIG. 4B is the second harmonic generation spectra of the
nonlinear optical crystals, Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 and
Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12, in accordance with some
embodiments of the present invention.
DETAILED DESCRIPTION
[0024] The following disclosure will discuss the way to use and
manufacture the embodiments. However, it should be recognized that
the present invention provides innovative concept in practice,
which can be presented by wide variety of specific contents. The
following discussion is intended to be illustrative and is not
intended to limit the scope of the present invention. The following
disclosure provides many different embodiments, or examples, for
implementing different features of the provided subject matter.
Specific examples of components and arrangements are described
below to simplify the present disclosure. These are, of course,
merely examples and are not intended to be limiting.
[0025] Embodiments relate to the nonlinear optical crystals and the
manufacturing method thereof are provided, which describe the
crystal structure, crystal data, manufacturing procedures and
operations of the nonlinear optical crystals.
[0026] The present invention discloses a nonlinear optical crystals
Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, wherein X=K or Rb. In one
embodiment, the formula of the nonlinear optical crystal is
Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 (LKTS). The space group was
determined as P4nc (No. 104) based on extinction conditions and
statistics of intensity distribution of the diffraction data which
were collected with a single crystal X-ray diffractometer. The
initial structural model was determined by direct method, then the
atomic positions and the atom displacement parameters were
calculated by the least-square refinement. Ti, Si and K atoms were
determined firstly and the remaining O and Li atoms were located in
the difference Fourier maps. The final cycles of the least-squares
refinement included the atomic positions and anisotropic atom
displacement parameters. The final refinement results were
R.sub.1=0.0130 and wR.sub.2=0.0393. The largest peak and hole in
the final difference Fourier maps were 0.243 e.ANG..sup.-3 and
-0.468 e.ANG..sup.-3, respectively.
[0027] In another embodiment, the formula of the nonlinear optical
crystal is L.sub.2Rb.sub.4TiOSi.sub.4O.sub.12 (LRTS). The space
group of LRTS was determined as P4nc (No. 104) based on the
extinction conditions and statistics of intensity distribution of
the diffraction data which were collected with a single crystal
X-ray diffractometer. The procedures of structural analysis were
similar to those for LKTS. The final refinement results were
R.sub.1=0.0179 and wR.sub.2=0.0397. The largest peak an hole in the
final difference Fourier maps were 0.488 e.ANG..sup.-3 and -0.468
e.ANG..sup.-3, respectively. The crystal data and structure
refinement results for LKTS and LRTS are shown in Table 1.
TABLE-US-00001 TABLE 1 Crystal data and structure refinement for
LKTS and LRTS Empirical formula Li.sub.2K.sub.4TiOSi.sub.4O.sub.12
(LKTS) Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12 (LRTS) Formula weight
538.54 724.02 Crystal system Tetragonal Tetragonal Space group P4nc
(No. 104) P4nc (No. 104) Unit cell dimensions a = 11.3336(5) .ANG.
a = 11.5038(6) .ANG. b = 11.3336(5) .ANG. b = 11.5038(6) .ANG. c =
5.0017(2) .ANG. c = 5.1435(3) .ANG. Volume 642.47(5) .ANG..sup.3
680.68(6) .ANG..sup.3 Z 2 2 Density (calculated) 2.784 Mg/m.sup.3
3.532 Mg/m.sup.3 F(000) 528 672 Theta range for data 2.54.degree.
to 28.29.degree. 2.50.degree. to 28.40.degree. collection Index
ranges -15 <= h <= 14 -15 <= h <= 14 -15 <= k <=
15 -15 <= k <= 14 -6 <= l <= 6 -6 <= l <= 6
Reflections collected 11697 6955 Independent reflections 793
[R(int) = 0.0194] 736 [R(int) = 0.0242] Goodness-of-fit on F2 1.222
1.218 Final R indices [I > 2sigma(I)] R.sub.1 = 0.0130, wR.sub.2
= 0.0393 R.sub.1 = 0.0179 wR.sub.2 = 0.03972 Absolute structure
parameter 0.04(3) 0.007(10) Extinction coefficient NA 0.0086(5)
Largest diff. peak and hole 0.243 and -0.468 e .ANG..sup.-3 0.488
and -0.570 e .ANG..sup.-3
[0028] FIG. 1 Illustrates an ORTEP drawing of the nonlinear optical
crystal structure, in accordance with some embodiments of the
present invention. The asymmetric unit of the nonlinear optical
crystal structure comprises a Ti atom, a Si atom, eight O atoms, a
Li atoms and a K atom (K can be replaced by Rb). The structure of
TiO.sub.5 square pyramid consists of a Ti atom and five O atoms and
the coordination number of Ti is five. A SiO.sub.4 tetrahedron
consists of a Si atom and four O atoms. The TiO.sub.5 square
pyramid and the SiO.sub.4 tetrahedron share one O atom.
[0029] FIG. 2A illustrates the top view of an ab plane of the
nonlinear optical crystal structure, in accordance with some
embodiments of the present invention. Each of the four corners of
the basal plane of TiO.sub.5 square pyramid is connected with an
adjacent SiO.sub.4 tetrahedron. The apical corners (O4 atom) of
TiO.sub.5 square pyramids are not connected with any SiO.sub.4
tetrahedron and are directed toward the same direction. Li and K
atoms (K can be replaced by Rb) are located at different sites in
the structural channels. FIG. 2B illustrates the connectivity
between TiO.sub.5 and a silicate chain in the crystal structure of
the nonlinear optical material, in accordance with some embodiments
of the, present invention. The silicate chain is formed by
SiO.sub.4 tetrahedra sharing two oxygen corners. Each of the four
corners in the basal plane of the TiO.sub.5 square pyramid is
connected with an adjacent SiO.sub.4 tetrahedron. FIG. 2C
illustrates the top view of an ac plane of the nonlinear optical
crystal structure, in accordance with some embodiments of the
present invention. The silicate chain is formed by SiO.sub.4
tetrahedra sharing two oxygen corners. Each of the four corners of
the basal plane of TiO.sub.5 square pyramid is connected with an
adjacent SiO.sub.4 tetrahedron. The apical corners (O4 atom) of
TiO.sub.5 square pyramids are not connected with any SiO.sub.4
tetrahedron and are directed toward the same direction, thus
forming a --Ti--O--Ti--O straight chain. Li and K atoms (K can be
replaced by Rb) are located at different sites in the structural
channels.
[0030] The specific embodiments of synthesizing the nonlinear
optical crystals LKTS and LRTS are described below. In one
embodiment, the nonlinear optical crystal LKTS was synthesized by a
flux method. The starting reagent LiF, KF, TiO.sub.2 and SiO.sub.2
were ground and mixed thoroughly. The molar ratio of Li:K:Ti:Si in
the starting reagent is a:b:1:1.about.4, wherein a and b are
between 10-30. In one embodiment, a=b=10. In another embodiment,
a=b=18. In another embodiment, a=b=20. In another embodiment,
a=b=25. In yet another embodiment, a=b=30. A mixture of LiF and KF
was used as the fluxes in the synthesis. The mixed starting reagent
is heated above the eutectic point of the flux. The eutectic
temperature of the mixed alkali metal fluorides can be found from
the phase diagram of LiF and KF. For example, when LiF and KF are
mixed in a 1:1 ratio, the melting point of the mixture is about
500.degree. C. The melting point of the mixture will be higher than
500.degree. C. if LiF and KF are mixed in any non- 1:1 ratio. In
other embodiments, a may be larger or smaller than b. Then, the
reaction mixture was slowly cooled down so that the nonlinear
optical crystal LKTS crystallized from the melt.
[0031] In some embodiments, the starting reagent LiF, KF, TiO.sub.2
and SiO.sub.2 was ground and mixed thoroughly. The molar ratio of
Li:K:Ti:Si in the starting reagent is 18:18:1:3. The reaction
mixture was contained in a Pt crucible, placed in a high
temperature furnace and heated to a first temperature. The first
temperature was between 650.degree. C. and 900.degree. C., such as
700.degree. C., 750.degree. C., 800.degree. C. or 850.degree. C.
The furnace was maintained at a temperature for several hours, such
as 6-24 hours. It is preferably 10-14 hours, such as 12 hours.
Then, the mixture was cooled to a second temperature at a slow
cooling rate. For example, the cooling rate was 0.2.degree. C./hr
to 5.degree. C./hr. It is preferably 0.2.degree. C./hr to 2.degree.
C./hr. The second temperature is between 550-700.degree. C., such
as 600.degree. C. or 650.degree. C. It is preferably
650-700.degree. C. Afterwards, the mixture was cooled to room
temperature by turning off the power of the furnace. Through
suction filtration, washing with water and ethanol and drying, the
product was obtained as colorless crystals along with a small
amount of white powder. The colorless crystals are LKTS and the
yield is 78%. The white powder is undissolved LiF.
[0032] In some embodiments, the nonlinear optical crystal LKTS was
synthesized by a hydrothermal method. The molar ratio of
LiOH.H.sub.2O:KOH:TiO.sub.2:SiO.sub.2:H.sub.2O in the starting
reagent was 2:10:1:4:10. The starting reagent was sealed in a gold
ampule, placed in a high-pressure vessel and heated to a third
temperature. The third temperature was between 450-550.degree. C.,
such as 500.degree. C. The reaction was performed under
supercritical hydrothermal conditions for 36-96 hours. It is
preferably 60-84 hours, such as 72 hours. Then, the mixture was
cooled down to a fourth temperature at a slow cooling rate. For
example, the cooling rate was 3.degree. C./hr to 8.degree. C./hr.
It is preferably 1.degree. C./hr to 6.degree. C./hr. It is better
2.degree. C./hr to 4.degree. C./hr. The fourth temperature is
between 300-350.degree. C., such as 310.degree. C., 320.degree. C.,
330.degree. C. or 340.degree. C. Afterwards, the pressure vessel
was cooled to room temperature by turning off the power of the
furnace. Through suction filtration, washing with water and ethanol
and drying, the product was obtained. as colorless crystals of
LKTS, as indicated by powder X-ray diffraction.
[0033] In another embodiment, the nonlinear optical crystal LRTS
was synthesized by a flux method. The starting reagents LiF, RbF,
TiO.sub.2 and SiO.sub.0 were around and mixed thoroughly. The molar
ratio of Li:Rb:Ti:Si in the starting reagent was c:d:1:1.about.4
wherein c and d were between 10-30. In one embodiment, c=d=10. In
another embodiment, c:d=17:19. In another embodiment, c=d=18. In
another embodiment, c=d=20. In another embodiment, c=d=25. In yet
another embodiment, c=d=30. A mixture of LiF and RbF was used as
the flux in the synthesis. The mixed starting reagents were
contained in a Pt crucible, heated above the eutectic point of the
flux. The eutectic temperature of the mixed starting reagent can be
obtained from the phase diagram of LiF and RbF. For example, when
LiF and RbF are mixed in a ratio of 17:19, the melting point of the
mixture is about 475.degree. C. The melting point of the mixture is
higher than 475.degree. C. if LiF and RbF are mixed in any non-
17:19 ratio. But in other embodiments, the ratio of c:d may not be
equal to 17:19. Then, the reaction mixture was slowly cooled so
that the nonlinear optical crystal LRTS crystallized from the
melt.
[0034] In some embodiments, the starting reagents LiF, RbF,
TiO.sub.2 and SiO.sub.2, were around and mixed thoroughly. The
molar ratio of Li:Rb:Ti:Si in the starting reagent is 17:19:1:3.
The reaction mixture was contained in a Pt crucible, placed in a
high temperature furnace and heated to a first temperature. The
first temperature was between 650.degree. C. and 900.degree. C.,
such as 700.degree. C., 750.degree. C. 800.degree. C. or
850.degree. C. The furnace was maintained at a temperature for
several hours, such as 6-24 hours. It is preferably 10-14 hours,
such as 12 hours. Then, the reaction mixture was cooled to a second
temperature at a slow cooling rate. For example, the cooling rate
was about 0.2.degree. C./hr to 5.degree. C./hr. It is preferably
about 0.2.degree. C./hr to 2.degree. C./hr. The second temperature
was between 550-700.degree. C. such as 600.degree. C. or
650.degree. C. It is preferably 550-700.degree. C. Afterwards, the
reaction mixture was cooled to room temperature by turning off the
power of the furnace. Through suction filtration, washing with
water and ethanol and drying, the product contained colorless
crystals of LRTS along with a small amount of white powder of
undissolved LiF, as indicated by powder X-ray diffraction.
[0035] Table 2a lists the ratio of the starting reagents of the
LKTS embodiments a-d in the present invention. The colorless
crystals and white powder were synthesized by the methods described
above. Then the composition of the colorless crystal obtained in
the embodiment c and the white powder of the embodiments a-d were
analyzed by the powder X-ray diffraction.
TABLE-US-00002 TABLE 2a The starting reagent ratio of LKTS analyzed
by powder X-ray diffraction Ratio of the starting reagent
Embodiments LiF KF TiO.sub.2 SiO.sub.2 LKTS a 18 18 1 1 b 18 18 1 2
c 18 18 1 3 d 18 18 1 4
[0036] FIG. 3A is the powder X-ray diffraction patterns of a
nonlinear optical crystal Li.sub.2K.sub.4TiOSi.sub.4O.sub.12, in
accordance with some embodiments of the present invention. The
pattern f of FIG. 3A is the theoretical powder pattern of the
nonlinear optical crystal LKTS. The pattern e of FIG. 3A is the
experimentally measured powder pattern of the colorless crystals.
The measured powder pattern is in good agreement with the
theoretical powder pattern.
[0037] In FIG. 3A, the powder patterns a-d correspond to the white
powder obtained from the embodiments a-d in Table 2a. In the powder
X-ray diffraction patterns, the diffraction peaks at about
2.theta.=39.degree. and 2.theta.45.degree. are due to LiF. The
white powders contains mainly undissolved LiF and other byproducts.
Quantitative analysis can be achieved by powder X-ray diffraction.
The relative amount of the components in a multi-phasic sample can
be determined by the relative intensity of the reflections in the
powder pattern. By comparing the powder patterns a-d of FIG. 3A, it
can be concluded that the LiF content of the embodiment c
(LiF:KF:TiO.sub.2:SiO.sub.2=18:18:3) is higher.
[0038] Table. 2b lists the ratio of the starting reagent of LRTS
embodiments a-d in the present invention. The colorless crystal and
white powder were synthesized by method described above. Then the
colorless crystal obtained in the embodiment c and the white powder
embodiments a-d were characterized by powder X-ray diffraction.
TABLE-US-00003 TABLE 2b The starting reagent ratio of LRTS analyzed
by powder X-ray diffraction Ratio of the starting reagent
Embodiments LiF RbF TiO.sub.2 SiO.sub.2 LRTS a 17 19 1 1 b 17 19 1
2 c 17 19 1 3 d 17 19 1 4
[0039] FIG. 3B is the powder X-ray diffraction patterns of the
nonlinear opitcal crystal Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12, in
accordance with some embodiments of the present invention. The
pattern f of FIG. 3B is the theoretical powder pattern of the
nonlinear optical crystal LKTS. The pattern of e of FIG. 3B is the
experimentally measured powder pattern of the colorless crystals.
The measured powder pattern is in good agreement with the
theoretical powder pattern.
[0040] In FIG. 3B, the powder patterns a-d correspond to the white
powder obtained from the embodiments a-d in Table. 2b. In the X-ray
powder diffraction patterns, the diffraction peaks at about
2.theta.=39.degree. and 2.theta.=45.degree. are due to LiF. The
white powder contains mainly undissolved LiF and other byproducts.
Quantitative analysis can be achieved by powder X-ray diffraction.
The relative amount of the components m a multi-phasic sample can
be determined by the relative intensity of the reflections in the
powder pattern. By comparing the powder patterns and of FIG. 3B, it
can be concluded that the LiF content of the embodiment c
(LiF:RbF:TiO.sub.2:SiO.sub.2-17:9:1:3) is higher.
[0041] FIG. 4A is the second harmonic generation spectra of the
nonlinear optical crystal Li.sub.2K.sub.4TiOSi.sub.4O.sub.12, in
accordance with some embodiments of the present invention and the
crystal KH.sub.2PO.sub.4 (KDP). FIG. 4B is the second harmonic
generation spectra of the nonlinear optical crystals
Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 and
Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12, in accordance with some
embodiments of the present invention. Second harmonic generation
(SHG), or known as frequency doubling, essentially produces a new
light source that its frequency is twice of the fundamental light.
The light intensity obtained by doubling the frequency. of the
laser at 1064 nm wavelength via commercial KDP powder is defined as
1. As shown in FIG. 4A, the wavelength intensity of nonlinear
optical crystal LKTS disclosed by the present invention is 10.1 in
comparison with KDP. In FIG. 4B, the intensity of LRTS is known as
13.1. Thus LKTS and LRTS both can produce strong SHG signals.
[0042] Comparing the laser-induced damage threshold of the
nonlinear optical crystal of the present invention with commercial
nonlinear optical crystals to test whether the nonlinear optical
crystals of the present invention can be applied to high power
laser without damage. From the experimental results, the
laser-induced damage threshold of LKTS and LRTS of the present
invention is high than 1.2 G-W/cm.sup.2, which is much higher than
the current commonly used commercial nonlinear optical crystals,
such as 0.4 GW/cm.sup.2 of KTiOPO.sub.4 (KTP), 0.5 GW/cm.sup.2 of
.beta.-Ba B.sub.2O.sub.4 (BBO) and 5 GW/cm.sup.2 of KDP. In
addition, LKTS and LRTS are stable up to 700.degree. C. based on
the results from high-temperature DSC/TGA measurements.
[0043] In accordance with embodiments of the present invention, a
new nonlinear optical crystal is provided, chemical formula of the
nonlinear optical crystal is Li.sub.2X.sub.4TiOSi.sub.4O.sub.12,
wherein X=K or Rb; the nonlinear optical crystal belongs to
tetragonal system, space group is P4nc, Z=2. The unit cell
parameters of Li.sub.2K.sub.4TiOSi.sub.4O.sub.12 are a=b=11.3336(5)
.ANG., c=5.0017(2) .ANG.; and the unit cell parameters of
Li.sub.2Rb.sub.4TiOSi.sub.4O.sub.12are a=b=11.5038(6) .ANG.,
c=5.1435(3) .ANG..
[0044] In accordance with embodiments of the present invention, a
method of manufacturing a nonlinear optical crystal including
mixing LiF, XF TiO.sub.2 and SiO.sub.2 to form a first starting
reagent; heating the first starting reagent to a first temperature
to melt the first starting reagent and to react; and cooling down
the first starting reagent from the first temperature to a second
temperature to crystallize a nonlinear optical material represented
by the formula Li.sub.2X.sub.4TiOSi.sub.4O.sub.12, wherein X=K or
Rb.
[0045] In accordance with embodiments of the present invention, a
method manufacturing a nonlinear optical crystal is provided,
including mixing LiOH.H.sub.2O, KOH, TiO.sub.2, SiO.sub.2 and
H.sub.2O to form a second starting reagent; heating the second
starting reagent to a third temperature to undergo a hydrothermal
reaction at the third temperature to form a supersaturated solution
comprising Li.sub.2K.sub.4TiOSi.sub.4O.sub.12; and cooling down the
second starting reagent from the third temperature to a fourth
temperature to crystallize a nonlinear optical material represented
by the formula Li.sub.2K.sub.4TiOSi.sub.4O.sub.12.
[0046] The advantage of the embodiments of the present disclosure
is to provide a new nonlinear optical crystal. The nonlinear
optical crystal material is easy to synthesize, thermally stable up
to 700.degree. C., generates strong second harmonic generation with
high laser-induced damage threshold.
[0047] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing front the spirit and scope of the present disclosure.
* * * * *