Optical device

Details Optical device Optical device

1998-04-24

2001-01-16

Font, Frank G. (Department: 2877)

Coherent light generators

Particular beam control device

Q-switch

C372S012000, C372S017000, C372S022000

Reexamination Certificate

active

06175578

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an optical device which causes laser oscillation by excitation with light of a laser activity ion-added optical crystal having nonlinear optical character and electric optical character, namely, an optical crystal having nonlinear optical character, electric optical character and laser activity, as well as generation of second harmonic and optical parametric oscillation, which are based on Q switching of laser and quasi-phase matching by the nonlinear optical character, in a path through the inside of the optical crystal.
BACKGROUND OF THE INVENTION
In this invention, each term means the following.
[Explanation of terms]
Period
In general, the term “period” inherently means a dimension of time. In this invention, however, it also means a dimension of length in a path through which a predetermined light passes inside an optical crystal.
Frequency
While the light is generally expressed by “wavelength”, it is expressed by “frequency” in this invention. The “wavelength” corresponding to this “frequency” varies depending on the material of transmission path, as in the case of radio waves.
Optical Parametric Oscillation
This means a phenomenon wherein two frequencies &ohgr;
s
and &ohgr;
i
are generated by excitation of quadratic polarization with a light wave having a frequency &ohgr;
p
. The relation of these frequencies is as expressed by the formula:
&ohgr;
p
=&ohgr;
s
+&ohgr;
i
.
Domain
A region wherein polarization in ferroelectrics occurs in the same direction. The references relevant to this invention include the following.
[References]
Reference 1
P. A. Franken, A. E. Hill, C. W. Peters, G. Weinreich, “Generation of optical harmonics”, Phys. Rev. Lett., 7, 118/1961.
Reference 2
J. A. Armstrong, N. Bleombergen, J. Ducuing and P. S. Pershen, “Interaction between light waves in a nonlinear dielectric”, Phys. Rev., 127, No. 6, 1918/1962.
Reference 3
Eikai Cho, Hiromasa Ito and Fumio Inaba, 49
th
Applied Physics Convention, “Experiment of nonlinear light waveguide having domain inversion structure”, 7a-ZD-9/1988.
Reference 4
E. J. Lim, M. M. Fejer, R. L. Byer, and W. J. Kozlovsky, “Blue light generation by frequency doubling in periodically poled lithium niobate channel waveguide”, Electron. Lett., 25, 731/1989.
Reference 5
J. Webjorn, F. Laurell, and G. Arvidsson, “Blue light generated by frequency doubling of laser diode light in a lithium niobate channel waveguide”, IEEE Photon. Tech. Lett., 1, 316/1989.
Reference 6
M. Yamada, N. Nada, M. Saitoh, and K Watanabe, “First-order quasi-phase matched LiNbO
3
waveguide periodically poled by applying an external field for efficient blue second-harmonic generation”, Appl. Phys. Lett., 62, 435/1993).
Reference 7
Y. Yamamoto, S. Yamaguchi, K. Suzuki, and N. Yamada, “Second-harmonic generation in a waveguide with domain-inverted regions like periodic lens sequence on z-face KTiOPO
4
crystal”, Appl. phys. Lett., 65, 938/1994.
Reference 8
Toshiaki Saihara, Masatoshi Fujimura and Hiroshi Nishihara, “Waveguide type SHG element by quasi-phase matching”, Journal of Electron Information Communication Convention, 76,597/1993.
Reference 9
S. Miyazawa, “Ferroelectric domain inversion in Ti-diffused LiNbO
3
optical waveguide”, J. Appl. Phys., 50, 4599/1979.
Reference 10
H. Ito, C. Takyu, and H. Inaba, “Fabrication of periodic domain grating in LiNbO
3
by electron beam writing for the application of nonlinear optical processes”, Electron. Lett., 27, 1221/1991.
Reference 11
Motoki Ohashi, Choichi Takyu and Koichi Taniguchi, “Studies of periodic domain inversion structure of ferroelectric nonlinear optical crystal by electron beam writing”, Journal of Electron Information Communication Convention Papers, C-I, J77-C-I, 383/1994.
Reference 12
S. Kurimura, M. Miura, and I. Sawaki, “New method of 20 mm-deep and 3.6 mm-periodic domain inversion for lst-order quasi-phase matching SHG in LiTaO
3
waveguides”, Conf. on Lasers and Electro-Optics, CPD5/1992.
Reference 13
Manabu Sato, Motoki Ohashi, Abedin Kaji Sarwar, Choichi Takyu and Masahiro Ito, “Bulk LiTaO
3
Domain Inversion Lattice by Electric Field Application Method”, Journal of Electron Information Communication Convention Papers, C-I, 366, J78-C-I, August/1995.
Reference 14
K S. Abedin, M. Sato, H. Ito, T. Maeda, K. Shimamura, and T. Fukuda, “Ordinary and extraordinary continuous wave lasing at 1.092 &mgr;m and 1.082 &mgr;m in bulk Nd: LiTaO
3
crystal”, J. Appl. Phys., 78,691, July/1995.
Reference 15
A. YARIV et al., OPTICAL WAVES IN CRYSTALS, pp.512-515, Table 12.2, WILEY-INTERSCIENCE, 1983.
Reference 16
Electric Communication Handbook, Ed. 25, First Division, 3·2, “Q switch”, Ohm Corp., March, 1979.
[Developmental history of optical device]
Subsequent to the invention of the laser, a technique for generating a second harmonic at 347 nm by ruby laser beam (694 nm) irradiation of rock crystal was disclosed in Reference 1.
Since then, nonlinear optics have been remarkably developed and have become an object of scientific studies, as well as a practical device technique in significant progress.
The development of light wave technique, as in the case of the development of radio wave technique, requires a light source having any wavelength, namely, a light source having any frequency. However, the wavelength of oscillation by laser is principally a specific wavelength determined by the material having a laser activity. Therefore, generation of a light having an optional wavelength, which cannot be obtained directly using a laser, is desired. As a technique for this end, a technique using a material having nonlinear optical character, namely, a nonlinear optical material, has been noticeably developed in recent years.
For an efficient generation of coherent light waves having different wavelengths by the use of a nonlinear optical material, namely, a material having nonlinear optical effect (to be referred to as nonlinear optical character in this invention), it is necessary to realize matching between the velocity at which a new wavelength component, namely, a frequency component, created by mixing plural light waves is polarized, and the transmission velocity of the light wave emitted by the polarization. The matching of the velocities is called phase matching and is generally achieved by the use of a crystal having a birefingence property.
There is a method to achieve phase matching without relying solely on the birefringence property, that is, a method free of limitations in conventional phase matching, and such phase matching method is called a quasi-phase matching. According to this method, the maximum value of a nonlinear optical coefficient component, namely, a nonlinear optical tensor component, can be utilized. The tensor component is disclosed in Reference 15. While the principle proposition of quasi-phase matching appears in Reference 2, due to the difficulty in rotating the optic axis z of a crystal (hereinafter “optical axis z”) periodically and precisely by 180° on a &mgr;m order, no specific device has been realized.
The inventor of this invention has disclosed, in Reference 3, a method for quasi-phase matching by a structure capable of periodic domain inversion by diffusion of impurities at periodic intervals on the surface of a material having ferroelectricity due to LiNbO
3
(lithium niobate), namely, a ferroelectric crystal. This periodic domain inversion structure can be manufactured by planar processing alone which is similar to that applied to a semiconductor device, and this structure achieves generation of second harmonic of a near infrared ray. Nearly at the time when the above-mentioned Reference 3 reported the technique, similar techniques were disclosed in Reference 4 and Reference 5, and improvements of these techniques were disclosed in References 6-8.
Moreover, the inventor of this invention has disclosed, in References 10, 11 and 13, a technique affording, with regard to a ferroelectric crystal, domain control with precision on a micron order, of a domain inversion structure

Affiliated with

Also associated with

Rating

Optical device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2553104