Design and fabrication of a resonant mirrors for locking blue laser diodes

The recent development and refinement of Gallium nitride (GaN) semiconductor devices has produced both blue light emitting diodes (LEDs) and laser diodes, which provide an efficient means to obtain high emission powers in the blue spectral range. Such sources have potential applications in both imaging and communication systems. However, many applications require precise control over the spectral emission from these devices and the current blue laser diodes lack this ability. In this paper, we demonstrate a method to control the spectral emission from GaN blue laser diodes. We present the simulation and subsequent fabrication of a guided-mode resonance filter (GMRF) that can be used to lock the output wavelength of a GaN blue laser diode. Successful locking of the emission wavelength with respect to fluctuations in the surrounding environment addresses challenges associated with communication systems. Our experiment uses an optical cavity with a GaN blue laser diode source and an on-axis narrowband GMRF fabricated for 445.2 nm. Based on spectral drift of the diode emission caused by an increase in input current, experimental measurements were taken with the GMRF installed to verify wavelength locking capability.