Coherent light generators – Particular resonant cavity – Folded cavity
Patent
1990-02-16
1992-07-07
Epps, Georgia Y.
Coherent light generators
Particular resonant cavity
Folded cavity
372 44, 372 45, H01S 3083
Patent
active
051289555
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a light amplifier, particularly to a ring laser diode.
2. Description of the Related Art
(Unpumped) annular optical waveguides or, respectively, optical ring oscillators are known from the prior art (JP published application 59-154086 and Appl. Phys. Lett. 47 (1985) Pages 439-440). Ring lasers to be optically pumped are described in Appl. Phys. Lett. 29 (1976) Pages 502-504 and 43 (1983) Pages 32-34. There is particular interest in annular laser arrangements to be pumped by current injection, what are referred to as ring laser diodes, whereby this principle of effecting the population inversion needed for the stimulated emission by current passage through a pn-junction of a semiconductor member is already disclosed by Heywang, DE-AS 12 98 216.
Ring laser diodes are disclosed by Jap. J. Appl. Phys. 16 (1977) Pages 2281-2282, 16 (1977) Pages 1395-1398; Appl. Phys. Lett. 36 (1980) Pages 801-803, 36 (1980) pages 353-355; Jour. Appl. Phys. 52 (1981) pages 4457-4461; Japanese published applications 58-118183 and 60-148185. These are ring laser diodes wherein the semiconductor material or, respectively, the semiconductor member is prepared such along or, respectively, in the region of such an annular zone. The aim of such preparations is to create an annularly fashioned index guidance as is known in equivalent fashion for straight-line index guidance of laser emission in laser diodes. For the sake of completeness, let it be pointed out here that the principle of gain guidance also exists for laser diodes having straight-line radiation propagation, whereby the necessary laser condition for this zone is created to a critical degree by topically concentrated current density distribution in a straight-line or, respectively, in an annular zone.
The preparation of a semiconductor member for the purpose of creating a ring laser diode is involved. This is probably one reason why ring laser diodes, insofar as known, have not been practically employed up to now, even though ring lasers advantageously do not require mirrors or surfaces having at least a certain reflectivity as are required for laser diodes having straight-line propagation of the laser emission.
SUMMARY OF THE INVENTION
It is an object of the present invention to specify an operation for such a light amplifier, particularly a ring laser diode, that can be manufactured in a technologically simpler way, particularly with at most a relatively slight adjustment outlay and that can be advantageously fashioned or, respectively, used as a multiplexer/demultiplexer. This object is achieved in a method for the operation of a light amplifier having an arcuately or annularly guided radiation path in a laser active material of the light amplifier, having a width (B) of an arcuate or annular pump zone provided on a surface of the laser active material that develops a pumped laser energy at a depth (D) in the laser active material, the pumped laser energy having a distribution profile with reference to a radiation path of mean radius (R.sub.0), and a gradient of the distribution profile of the pumped laser energy effecting a gradient of the refractive index (n) of the laser active material dependent thereon, and a maximum gain (g.sub.max) lying at a center radiation frequency (f.sub.0), the method of operation being characterized by generating a phase guided laser radiation having a frequency f.sub.1,2 =f.sub.0 .+-..DELTA.f, the phase guided radiation having a gain less than the maximum gain depending upon the width of the pump zone and the depth in the material of the laser energy, and allowing the phase guided radiation to circulate in a radius region (R.sub.0 .+-..DELTA.R) which is established for the center radiation frequency in which a refractive index n(R)=n.sub.0 .+-..DELTA.n is modified by the pumped laser energy to provide a refractive index curve approximated to the negative inverse of the radius of the radiation path (-1/R) so that radiation analogous to Tscherenkow
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Epps Georgia Y.
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