Coherent light generators – Particular active media – Insulating crystal
Reexamination Certificate
2000-06-09
2003-09-23
Scott, Jr., Leon (Department: 2828)
Coherent light generators
Particular active media
Insulating crystal
Reexamination Certificate
active
06625186
ABSTRACT:
RELATED FIELD OF THE INVENTION
The present invention relates to a laser frequency doubling device of the Re Ca
4
O (BO
3
)
3
, ReCOB for short (Re═Gd, Y) crystal with specific cut angles. It belongs to the field of optoelectronics.
ReCOB discovered by Aka etc. is a type of artificial nonlinear optical crystals. It has been found that YCOB and GdCOB crystals have the features of the larger nonlinear optical effect (which comparable to LiB
3
O
5
crystal) and easy growth. The typical size of the crystal is up to &phgr;50×100 mm. It has been also found that the red, green and blue visible laser can be effectively generated by the two crystals through doubling the frequency of 1340 nm, 1064 nm, 1053 nm, 940 nm laser. In addition, since the ions Gd and Y of the two crystals can be easily replaced by the stimulated ions Nd, and Yb, the self-frequency doubling crystal of Nd: YCOB, Yb: YCOB or the like can be formed. The self-frequency doubled output of the crystals can be up to 50 mw. Therefore, Nd: YCOB and Yb: YCOB are also self-frequency doubling crystal materials. Widespread interest in the above-mentioned materials has been attracted in the science and technology circles because of the advantages of the materials.
BACKGROUND OF THE INVENTION
The ReCOB crystal which belongs to the monoclinic m point group is the lowest symmetry crystal among the all practical nonlinear crystal materials, also is one of the lowest symmetry crystals in all the nonlinear crystals known so far. According to the crystal point group symmetry, the nonlinear optical coefficients d
ij
(i=1-3, j=1-6, wherein 1→11, 2→22, 3→33, 4→23, 5→13, 6→12,) have as many as 8 non-zero components. Considering that the frequency-doubling coefficients should obey the Kleinman symmetry condition, this type of crystals has still 6 independent d
ij
coefficients, i.e. d
33
, d
11
, d
32
, d
12
, d
13
and d
31
. In principle 4 coefficients d
33
, d
11
, d
31
, d
13
can be measured by the Maker fringes method, while d
32
, d
13
can be measured by phase-matching method. However, the frequency-doubling coefficients of these crystals have not been determined until now. Therefore, it is difficult to calculate the effective frequency-doubling coefficients of the crystals, and to determine further the optimum cut angles for the fabrication of the frequency-doubling devices. Japanese scientists have determined the preliminary effective frequency doubling coefficient of the YCOB crystal at the orientation of &thgr;=33° and &phgr;=9° in 1997. Most of scientists now believe that the optimum phase matching orientation (i. e. The largest effective frequency-doubling coefficient is in this orientation) is &thgr;=33° and &phgr;=9°. The new result of the self-frequency doubling experiments of Nd:YCOB also indicated that this is the optimum phase-matching orientation. However, the theoretical calculation and the experimental measurement demonstrated that the orientation of &thgr;=33° and &phgr;=9° is not the optimum phase-matching orientation for YCOB.
SUMMARY OF THE INVENTION
The object of the present invention is to find the optimum cut orientation of the ReCOB crystal for the fabrication of laser frequency doubling device, such that the laser frequency-doubling devices fabricated from the ReCOB crystal with specific cut angles according to the present invention have larger frequency-doubling conversion efficiency than that according to the prior technique.
The main content of the present invention is to determine optimum cut orientation of the ReCOB crystal frequency-doubling device for the incident laser beam of 1340 nm, 1064 nm, 1053 nm, 940 nm. The device cut-angles are as following:
(1) The device cut-angles are: &thgr;
1
=(67.0±5.0)°, &phgr;
1
=(27.5±5.0)° or &thgr;
2
=(67.0±5.0)°, &phgr;
2
=(152.5±5.0)°, when the frequency-doubling crystal is YCOB, &lgr;
&ohgr;
=134 nm;
(2) The device cut-angles are: &thgr;
1
=(65.9±5.0)°, &phgr;
1
=(36.9±5.0)° or &thgr;
2
=(66.3±5.0)°, &phgr;
2
=(143.5±5.0)°, when the frequency-doubling crystal is YCOB &lgr;
&ohgr;
=1064 nm;
(3) The device cut-angles are: &thgr;
1
=(65.0±5.0)°, &phgr;
1
=(37.1±5.0)° or &thgr;
2
=(65.7±5.0)°, &phgr;
2
=(142.9±5.0)° when the frequency-doubling crystal is YCOB, &lgr;
&ohgr;
=1053 nm;
(4) The device cut-angles are: &thgr;
1
=(64.4±5.0)°, &phgr;
1
=(44.8±5.0)° or &thgr;
2
=(66.8±5.0)°, &phgr;
2
=(135.3±5.0)° when the frequency doubling crystal is YCOB, &lgr;
&ohgr;
=940 nm;
(5) The device cut-angles are: &thgr;
1
=(64.5±5.0)°, &phgr;
1
=(34.4±5.0)° or &thgr;
2
=(66.5±5.0)°, &phgr;
2
=(145.7±5.0)° when the frequency-doubling crystal is GdCOB, &lgr;
&ohgr;
=1340 nm;
(6) The device cut-angles are: &thgr;
1
=(62.0±5.0)°, &phgr;
1
=(47.8±5.0)° or &thgr;
2
=(67.0±5.0)°, &phgr;
2
=(132.6±5.0)° when the frequency-doubling crystal is GdCOB, &lgr;
&ohgr;
=1064 nm;
(7) The device cut-angles are: &thgr;
1
=(62.0±5.0)°, &phgr;
1
=(48.7±5.0)° or &thgr;
2
=(67.0±5.0)°, &phgr;
2
=(131.7±5.0)° when the frequency-doubling crystal is GdCOB, &lgr;
&ohgr;
=1053 nm;
(8) The device cut-angles are: &thgr;
1
=(60.5±5.0)°, &phgr;
1
=(61.5±5.0)° or &thgr;
2
=(68.0±5.0)°, &phgr;
2
=(119.9±5.0)° when the frequency-doubling crystal is GdCOB, &lgr;
&ohgr;
=940 nm.
Using anion group theory, the present invention calculated for the first time the frequency-doubling coefficients of YCOB and GdCOB crystals. Table 1 lists theoretical d
ij
values calculated respectively by Gaussian 92 and CNDO quantum chemistry programs based on the anion group theory for YCOB and GdCOB. Table 1 also lists d
33
and d
32
values of the YCOB crystal, d
33
value of the GdCOB crystal and other d
ij
values measured by the Maker fringes method. The agreement between the experimental values and the theoretical values are excellent. Furthermore, it is determined by the symmetry theory that the phase-matching orientation of ReCOB have mmm space symmetry (m is perpendicular to refractive principal axes X.Y.Z respectively). Therefore, with only one space quadrant for example the first quadrant (0°≦&thgr;≦90°, 0°≦&phgr;≦90°) all device cut-angle orientations can be found by mmm symmetry. With symmetrical theory it is also determined that the effective frequency-doubling coefficient d
eff
has the 2/m (m⊥Y) space symmetry. Therefore, in the first and second quadrants, d
eff
values are independent. Once d
eff
values are determined in the two quadrants the d
eff
values in all phase-matching space can be found by symmetry 2/m, i.e. once the orientations of the largest d
eff
values are found in the first and second quadrants, the optimum frequency doubling-orientations of the whole space can be found.
TABLE 1
the frequency-doubling coefficients of YCOB
and GdCOB crystals (unit: pm/V)
Measured value by
Calculated value
Maker fringes
Crystal
d
ij
Gauss 92
CNDO
method
YCOB
d
33
−1.018
−1.236
+0.92
d
11
−0.104
0.056
≈0
d
12
−0.015
0.128
<<d
32
d
13
−0.253
−0.186
<<d
33
d
31
0.120
0.151
<<d
33
d
32
0.757
1.081
±1.34
GdCOB
d
33
−0.903
−1.14
±0.5761
d
11
0.050
0.050
≈0
d
12
0.128
0.166
≈0
d
13
−0.183
−0.22
<<d
33
d
31
0.127
0.16
≈0
d
32
0.741
1.00
±0.6846
Taking the four conventional laser wavelength 1340 nm, 1064 nm, 1053 nm, 940 nm for examples (using the determined d
ij
values and the refraction dispersion relation), the present invention has calculated the d
eff
distribution in the first and second quadr
Chen Chuangtian
Hu Xiaobo
Jiang Jie
Jiang Minhua
Lin Jiao
Jr. Leon Scott
Shandong University
Venable LLP
LandOfFree
Laser frequency doubling device of ReCa4O(BO3)3 crystal with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laser frequency doubling device of ReCa4O(BO3)3 crystal with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser frequency doubling device of ReCa4O(BO3)3 crystal with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3019571