Miniaturized blue laser using second harmonic generation

We demonstrate a miniaturized blue laser (5 x 12 x 1.5 mm(3)) using second harmonic generation (SHG), which consists of a quasi-phase-matched (QPM)-SH G waveguide device on an x-cut Mg-doped LiNbO3 substrate and a tunable dist ributed-Bragg-reflector (DBR) laser diode. By using the QPM-SHG waveguide d evice on an x-cut substrate, efficient optical coupling was realized withou t a half-wave plate, and the maximum coupling efficiency of 75% was achieve d. 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 mecha nical 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 degrees C. We succeeded in downsizing the SHG blue laser to 0.1 cm(3), which is suf ficiently small for its application to optical disk systems.