Conversion Efficiency Enhancement Technique for a Quasiphase Matched Second-Harmonic Generation Device

Abstract

Conversion efficiency enhancement techniques have been demonstrated for quasiphase matched (QPM) second-harmonic generation (SHG). First, we describe a technique for confining the high fundamental optical power density in a waveguide with a domain-inverted grating (SHG waveguide), i.e., a technique for monolithic integration, the SHG waveguide, and a distributed Bragg reflector (DBR). A 40% increase in the conversion compared with a conventional device without a DBR was achieved under QPM conditions. We also describe a method of automatically satisfying QPM conditions, using a laser diode (LD) with antireflection-coated facets. We used the InP/InGaAsP LD and confirmed that the LD oscillated at a wavelength satisfying the QPM conditions. The normalized conversion efficiency was 4.1%·W-1·cm-2.