Abstract

The conversion efficiency for waveguide-mode second-harmonic generation (SHG) with detuned intersubband transitions in asymmetric double quantum wells (ADQW) is optimized theoretically and compared with results for surface incidence. The analysis includes the effects of absorption, saturation of the absorption and SHG, pump depletion, optical carrier heating, mode confinement and completion, and the, loss of phase coherence due to waveguide, bulk, and resonant intersubband contributions to the mismatch of the refractive indices at the pump and second-harmonic frequencies. ADQWs with the optimum degree of detuning derived from a balance between low absorption losses, sufficient nonlinear susceptibility, and adequate compensation of the refractive index mismatch to maintain phase coherence have been determined for structures employing GaAs/AlGaAs, InGaAs/InAlAs and GaSb/InGaSb/AlGaSb material systems, all subject to the constraint that the epitaxial growth thickness should not exceed 10 μm. In the best GaAs/AlGaAs ADQWs, the maximum attainable conversion efficiency at high intensities is limited by the electron transfer to X-valley states whenever the T-valley offsets are large enough to permit optimal detuning.

© 1996 Optical Society of America