Measurement of the nonlinear coefficient of orientation-patterned GaAs and demonstration of highly efficient second-harmonic generation
Quasi-phase-matched (QPM) GaAs structures, 0.5 mm thick, 10 mm long, and with 61-mum grating periods, were grown by a combination of molecular-beam epitaxy and hydride vapor phase epitaxy. These were characterized by use of mid-IR second-harmonic generation (SHG) with a ZnGeP2 (ZGP) optical parametric oscillator as a pump source. The SHG efficiencies of QPM GaAs and QPM LiNbO3 were directly compared, and a ratio of nonlinear coefficients d14(GaAs)/d33(LiNbO3) = 5.01 plus-or-minus 0.3 was found at 4.1-mum fundamental wavelength. For input pulse energies as low as 50 muJ and approximately60-ns pulse duration, an internal SHG conversion efficiency of 33% was measured in QPM GaAs.