Coherent light generators – Particular resonant cavity – Specified cavity component
Patent
1998-12-23
2000-10-17
Font, Frank G.
Coherent light generators
Particular resonant cavity
Specified cavity component
372 99, 372 19, 372 9, 372 28, 372 29, 372 32, 372 92, 372 98, 372108, 307 88, 307 3, H01S 308
Patent
active
061342599
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to lasers and optical resonators.
BACKGROUND OF THE INVENTION
In general, it is desirable that lasers be compact in size while, at the same time, producing a high power, high quality output beam. Unfortunately, in many laser systems such desired requirements cannot all be fulfilled simultaneously, so design compromises must be made.
The characteristics of the output beam depend on the distribution of the light inside the optical resonator of the laser. The light inside an optical resonator is distributed in well defined patterns termed modes.
The optical quality of the output beam from an optical resonator is determined by its divergence, which differs for each mode within the resonator. The highest quality output beam has the least divergence.
A parameter which provides a quantitative measure for the output beam is called M.sup.2. This parameter is described in A. E. Siegman, New developments in laser resonators, SPIE Vol. 1224, 2-14 (1990), the disclosure of which is hereby incorporated by reference.
The optimal shape of the output beam with the least divergence is the Gaussian shape, where M.sup.2 =1. Output beams with larger M.sup.2 parameters have greater divergence, so their resulting beam quality is inferior. If only a single mode is present inside the resonator, then the output beam from the resonator can be improved by placing outside the optical resonator a compensating optical element, designed especially to improve the divergence for that mode.
The field distribution of the modes affects the power of the beam emerging from the resonator. One of the most common ways to describe this field distribution is using a cylindrical representation as described in the following publications:
A. G. Fox and T. Li, Resonant modes in an optical maser, Bell Sys. Tech. J., Vol. 40, 453-488 (1961).
H. Kogelnik and T. Li, Laser beams and resonators, Proc. IEEE, Vol 54, No 10, 1312-1328 (1966).
The field distribution is expressed as follows: the angular factor describing the angular distribution of the mode, M is the radial factor describing the radial distribution of the mode and R could be an arbitrary complete set of orthogonal functions.
There are known several techniques to 1) change the field distribution of the modes, 2) achieve mode discrimination and 3) increase the output power. These techniques are briefly described hereinbelow: by the reflectors and the lenses that are incorporated into the optical resonator. Typically, the shape of these elements is spherical, and the field distribution of the resulting modes is well known as described, in H. Kogelnik and T. Li, Laser beams and resonators, Proc. IEEE, Vol 54, No 10, 1312-1328 (1966).
Recently, new types of reflectors have been introduced in order to control the field distribution of the modes. These reflectors are independent of angular coordinates but dependent on radial coordinate. Consequently, they can control only the radial field distribution of the modes. Reflectors of this type are described in P. A. Belanger, P. L. Lachance and C. Pare, Super-Gaussian output from a CO.sub.2 laser by using a graded phase mirror resonator, Opt. Let, Vol. 17, No. 10, 739-741 (1992). reduced, even to a single mode, by introducing an aperture inside the resonator. A parameter that describes the relative aperture width is called the Fresnel number. The Fresnel number is defined by the following expression: ##EQU1## where a is the radius of the aperture, L is the length of the optical resonator and .lambda. is the wavelength of the mode.
When the Fresnel number is small, corresponding to a small aperture, only the mode with the narrowest field distribution propagates while the rest of the modes suffer a large increase in loss of intensity and cease to exist. In such a situation, single mode operation can be easily achieved, thereby discriminating it from the other modes. The quality of the resulting output beam is high, with corresponding relatively low M.sup.2. Unfortunately, such a configuration, having a sm
REFERENCES:
patent: 4088898 (1978-05-01), Stitch
patent: 5283796 (1994-02-01), Fink
A.E. Siegman, SPIE vol. 1224 Optical Resonators, pp. 2-14, 1990.
A.G. Fox et al., Bell System Technical Journal, 40:453-488, 1961.
H. Kogelnik et al., Proc. of the IEEE, 54, 54:1312-1328, 1966.
P.A. Belanger et al., Optics Letters, 17:739-741, 1992
L.W. Casperson et al., Optics Communications, 21:1-4, 1977.
A.E. Siegman, Optics Letters, 18:675-677, 1993.
E. Hasman et al, Optics Letters, 16:423-425, 1991.
N. Davidson et al., Applied Optics, 31:1067-1073, 1992.
Danziger Yochay
Davidson Nir
Hasman Erez
Flores Ruiz Delma R.
Font Frank G.
Yeda Research and Development Co. Ltd.
LandOfFree
Optical resonator with spiral optical elements 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 resonator with spiral optical elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical resonator with spiral optical elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-476590