Method and Laser Device for Stabilized Frequency Doubling
A system and method for emitting a plurality of second harmonic light frequencies that is generally unaffected by small variations in external cavity length and temperature. An illustrative embodiment provides a laser system that comprises a semiconductor gain region operating within the coherence collapse regime, an intra-cavity nonlinear optical medium, and a feedback reflector. The semiconductor gain region operates in the coherence collapse regime and produces broad frequency fundamental light, the nonlinear resonator doubles a first portion of the broad frequency fundamental light and emits a plurality of second harmonic light frequencies external to the laser system. A second portion of the broad frequency fundamental light is reflected into the semiconductor gain region with a feedback power ratio sufficient to cause the semiconductor gain region to operate in the coherence collapse regime.
1 . A method of generating a plurality of second harmonic light frequencies in an intra-cavity laser comprising:
operating a laser gain region in coherence collapse;
producing a broad frequency fundamental light in the laser gain region;
feeding back a first portion of the broad frequency fundamental light into the laser gain region;
doubling a second portion of the broad frequency fundamental light to form a plurality of second harmonic light frequencies; and
emitting from the intra-cavity laser the plurality of second harmonic light frequencies.
2 . The method of claim 1 , wherein the broad frequency fundamental light is in an infrared frequency range.
3 . The method of claim 1 , wherein the plurality of second harmonic light frequencies are within a visible frequency range.
4 . The method of claim 1 , wherein the plurality of second harmonic light frequencies are within a green frequency range.
5 . The method of claim 1 , wherein the first portion of the broad frequency fundamental light has a feedback power ratio between about −45 db and about −5 db.
6 . The method of claim 1 , wherein the laser gain region is a semiconductor laser selected from the group consisting of an edge emitting laser, a grating outcoupled surface emitting (GSE) laser, and a vertical cavity surface emitting (VCSEL) laser.
7 . The method of claim 1 , wherein doubling a second portion of the broad frequency fundamental light to form a plurality of second harmonic light frequencies is accomplished in a nonlinear optical medium.
8 . The method of claim 7 , wherein the nonlinear optical medium is a nonlinear crystal resonator.
9 . An intra-cavity laser system comprising:
a semiconductor gain region operating in the coherence collapse regime and producing a broad frequency fundamental light;
a nonlinear resonator optically coupled to the semiconductor gain region, wherein the nonlinear resonator doubles a first portion of the broad frequency fundamental light and emits a plurality of second harmonic light frequencies external to the intra-cavity laser system; and
a coherence collapse reflector optically coupled to the nonlinear resonator and to the semiconductor gain region, wherein a second portion of the broad frequency fundamental light is reflected into the semiconductor gain region with a feedback power ratio sufficient to cause the semiconductor gain region to operate in the coherence collapse regime.
10 . The intra-cavity laser system of claim 9 , further comprising:
an anti-reflective coating on an emitting surface of the semiconductor gain region.
11 . The intra-cavity laser system of claim 9 , wherein the plurality of second harmonic light frequencies are within a visable frequency range.
12 . The intra-cavity laser system of claim 9 , wherein the plurality of second harmonic light frequencies are within a green frequency range.
13 . The intra-cavity laser system of claim 9 , wherein the feedback power ratio causing the semiconductor gain region to operate in the coherence collapse regime is between about −40 db and about −5 db.
14 . The intra-cavity laser system of claim 9 , wherein the semiconductor gain region is selected from the group consisting of an edge emitting laser, a grating outcoupled surface emitting (GSE) laser, and a vertical cavity surface emitting (VCSEL) laser.
15 . The intra-cavity laser system of claim 9 , wherein the nonlinear resonator is a monolithic ring resonator.
16 . The intra-cavity laser system of claim 9 , wherein the nonlinear resonator comprises a nonlinear crystal and a set of discrete reflectors.
17 . The intra-cavity laser system of claim 9 wherein the nonlinear resonator is selected from the group consisting of a standing wave resonator, a triangle ring resonator, and a bow-tie ring resonator.
18 . A method of operating a laser system for generating a plurality of third harmonic light frequencies in an intra-cavity laser comprising:
operating a laser gain region in coherence collapse;
producing a broad frequency fundamental light in the laser gain region;
feeding back a first portion of the broad frequency fundamental light into the laser gain region;
tripling a second portion of the broad frequency fundamental light to form a plurality of third harmonic light frequencies; and
emitting from the intra-cavity laser the plurality of third harmonic light frequencies.
19 . The method of operating an intra-cavity laser system of claim 18 , wherein the nonlinear resonator is selected from the group consisting of a standing wave resonator, a triangle ring resonator, and a bow-tie ring resonator.
20 . The method of operating an intra-cavity laser system of claim 18 , wherein the semiconductor gain region is selected from the group consisting of an edge emitting laser, a grating outcoupled surface emitting (GSE) laser, and a vertical cavity surface emitting (VCSEL) laser.