Patent ID: 7248618

Claim:
Apparatus for intra-cavity doubling of the emission frequency of a laser diode, the apparatus comprising: a laser diode having a front facet, a back facet opposite the front facet, and a gain medium, wherein the laser diode emits first laser light from the front facet thereof, the first laser light having a fundamental frequency and a first spectral bandwidth; a Bragg grating element comprising a three-dimensional glass element having a non-dispersive Bragg grating formed therein; and a quasi-phase-matched nonlinear optical device positioned between the Bragg grating element and the front facet of the laser diode, the nonlinear optical device having an acceptance bandwidth, wherein the nonlinear optical device receives at least a portion of the light emitted by the laser diode, generates a second harmonic of the received light, and directs at least a portion of the second harmonic into the Bragg grating element; wherein the Bragg grating element retro-reflects light having the fundamental frequency back into the nonlinear optical device and allows light of the second harmonic to pass through, the retro-reflected light having a bandwidth that is less than the acceptance bandwidth of the nonlinear optical device; and wherein the Bragg grating element causes the laser diode to emit second laser light having the fundamental frequency and a second spectral bandwidth that is more narrow than the acceptance bandwidth of the nonlinear optical device.