Systems and methods for second harmonic generation using three-dimensional Bragg grating elements

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.