Enhanced nonlinear optical response of InP(100) membranes

The nonlinear optical response of porous InPs100d membranes was examined and compared to that of bulk crystalline s100d-oriented InP. Measurements of optical rectification and optical second-harmonic generation have been carried out in reflection under excitation by 120 fs, 800 nm Ti:Sapphire laser beam pulses. A significant enhancement in both the radiated terahertz field and second-harmonic radiation from the porous InPs100d surface, relative to the bulk InPs100d surface, was observed. Terahertz field polarization measurements indicate that the enhancement is primarily on the component of the radiated field related to optical rectification as opposed to photocarrier-related effects. It is suggested that the enhanced nonlinear optical response is related to strong enhancements of the local field within the porous network.