Miniaturized Blue Laser using Second Harmonic Generation

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Abstract
We demonstrate a miniaturized blue laser (5×12×1.5 mm3) using second harmonic generation (SHG), which consists of a quasi-phase-matched (QPM)-SHG waveguide device on an x-cut Mg-doped LiNbO3 substrate and a tunable distributed-Bragg-reflector (DBR) laser diode. By using the QPM-SHG waveguide device on an x-cut substrate, efficient optical coupling was realized without a half-wave plate, and the maximum coupling efficiency of 75% was achieved. The blue light power of 2 mW was generated for the fundamental coupling power of 20 mW, which agreed with a conversion efficiency of 10%. The mechanical stability of the planar-type butt-coupled SHG blue laser was examined, where the coupling efficiency was maintained constantly under the change of module temperature and the temperature cycle test from 10 to 60°C. We succeeded in downsizing the SHG blue laser to 0.1 cm3, which is sufficiently small for its application to optical disk systems.