Kenchi ITO, Kazumi KAWAMOTO and Hiroshi MOMIJI

Central Research Laboratory, Hitachi, Ltd., P.O. Box 2, Kokubunji, Tokyo, 185 Japan

(Received July 20, 1995; Accepted August 7, 1995)

The characteristics of intra-cavity distributed Bragg reflector (DBR) quasi-phase-matched (IDQPM) second-harmonic-generation (SHG) lasers are theoretically studied. In the IDQPM-SHG laser, a QPM device and a DBR for feedback are separately fabricated on the same substrate with the QPM device placed between the DBR and a semiconductor laser. The threshold current of the IDQPM-SHG laser depends on the coupling efficiency between the laser diode and the QPM waveguide and the reflectivity of the DBR. The SH output of the IDQPM-SHG laser is strongly dependent on the generalized SHG conversion efficiency, κ. This laser has the potential to attain an SH output over a 30-mW using a currently available 50-mW semiconductor laser for the fundamental light source, when highly efficient QPM device (κ=2.2 W^?1) is used. Its tolerance for various deviations from the initial design and the problems to develop a commercially available IDQPM-SHG laser are also discussed.

Key words : second harmonic generation (SHG), waveguide, quasi-phase-matching (QPM), distributed Bragg reflector (DBR), intra-cavity