Frequency-doubled laser

Details Frequency-doubled laser Frequency-doubled laser

1992-01-23

1993-09-28

Scott, Jr., Leon

Coherent light generators

Particular beam control device

Nonlinear device

372 21, 372 98, 359328, H01S 310

Patent

active

052491900

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a laser of the type which has a pumped light source and a resonator.
Many interesting lasers provide laser light whose wavelengths are useless, or poorly suited, for many applications. Visible laser light is required specifically for optical applications. For example, an Nd-YAG laser provides laser radiation with a wavelength of 1064 nm. Attempts have therefore been made to convert this laser light into visible light by frequency doubling.
Numerous proposals are known for how to obtain a frequency doubling of laser light. For example, a nonlinear crystal inside or outside a resonator is used. The laser light is coupled into the crystal and at the output of the crystal one obtains laser radiation with a double frequency. However, the intensity of the double-frequency light has a relatively lo ratio to the intensity of the light with the original laser frequency; this ratio depends on the intensity of the laser light with the fundamental wavelength that passes into the crystal.
In view of this fact there have been consistent attempts up to now to dispose the nonlinear crystal in a place where there is a considerable concentration of intensity. For example, DE-OS 36 43 648 proposes giving the output mirror disposed beside the nonlinear crystal a concave, partly mirror-coated surface in order to obtain an optimal beam shaping in the resonator. The concave mirror surface is intended to obtain a focusing of the radiation.
In virtually all known proposals for a frequency-doubled laser the output mirror is designed as a concave mirror in the neighborhood of the nonlinear crystal.
Nevertheless, the yield of frequency-doubled light is relatively low. There are fluctuations in intensity which have a particularly serious effect in the continuous wave mode. High intensity Peaks can be observed.
There are a number of theoretical and practical investigations on the causes for such intensity fluctuations and how to eliminate them.
However, these efforts to eliminate the intensity fluctuations totally or at least in part have had no decisive success up to now.
The invention is based on the problem of providing a laser of the type stated at the outset that shows only small intensity fluctuations in the frequency-doubled radiation while having high efficiency.
This problem is solved by the present invention which fundamentally involves two alternative possibilities. Firstly, it is regarded as imperative to fix a clear polarization of the fundamental wave in the resonator with the aid of a polarizer since this is a precondition for stable operation. The polarizer is disposed between the nonlinear crystal and the laser medium.
In a first embodiment of the invention the output mirror is designed as a plane mirror or an approximately plane mirror. The invention thus expressly departs from the concave output mirror that has hitherto been regarded as virtually imperative in the expert world. While the arrangement of the nonlinear crystal in the area of the focus of the concave output mirror used to be regarded as virtually imperative, the design of the laser according to the present invention dispenser with the maximum light intensity in the center of the nonlinear crystal. However, this is more than compensated for by a gain that is due to the avoidance of an undesirable shift of rays within the nonlinear crystal. This is explained in more detail in the following.
Light passing into the nonlinear crystal is generally divided, as is well-known, into two extraordinary rays which are polarized perpendicular to each other. In the special case of uniaxial crystals these are the well-known ordinary and extraordinary component rays. With the type II frequency doubling treated here the intensities of the two rays are about equal since the polarizer preceding the crystal polarizes the light in a direction that forms an angle of 45.degree. with the two polarizing directions. The two rays obey different laws of calculation and are deflected laterally relative to each other, emerging from the crystal in stagg

REFERENCES:
patent: 3619637 (1971-11-01), Goto
patent: 4739507 (1988-04-01), Byer et al.
patent: 5030851 (1991-07-01), Unternahrer
patent: 5047668 (1991-09-01), Rosenberg
patent: 5084879 (1992-01-01), Suzuki et al.
Perkins, P. E. and Driscoll, T. A.: "Efficient Intracavity Doubling in Flash-Lamp Pumped Nd:YLF", J. Opt. Soc. Am. B, vol. 4, No. 8, Aug., 1987, pp. 1281-1285.
Huth, G. B. and Kuizenga, D.: "Green Light from Doubled Nd:YAG Lasers", Lasers & Optronics, No. 10, Oct., 1987, pp. 59-61.
Hanna, D. C., Kazer, A. and Shepherd, D. F.: "Active Mode-Locking and Q-Switching of a 1.54 .mu.m Er: Glass Laser Pumped by a 1.064 .mu.m Nd:YAG Laser", Optics Communications, vol. 65, No. 5, Mar. 1, 1988, pp. 355-357.
Burnham, R. and Hays, A. D.: "High-Power Diode-Array-Pumped Frequency-Doubled cw Nd:YAG Laser", Optics Letters, Optical Society of America, vol. 14, No. 1, 1989, pp. 27-29.
Weber, H.: "Laserresonatoren und Strahlqualitat-Resonators and Beam Quality", Laser und Optoelektronik, No. 2, 1988, pp. 60-66.

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