Bulk n-InP wafers and porous membrances with (111) crystallographic orientation have been illuminated with 120 fs pulses of 800 nm radiation from a Ti:Sapphire amplified laser system. Terahertz (THz) emission from samples was measured as a function of excitation fluence in the reflection geometry. It was established that the THz emission from both bulk and porous InP (111) saturates at high excitation fluence, emitting comparable levels of far-infrared radiation. Below saturation, however, the emission from the porous InP (111) membrane was found to be approximately an order of magnitude greater in radiated electric field or approximately two orders of magnitude in power relative to the bulk sample. The observed increase in efficiency from the porous, relative to the bulk samples, can be attributed either to the local field enhancement in the porous network for the nonlinear contribution to the radiated THz fields, or to modifications of the transient currents resulting in enhanced THz radiation.
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Reid et al. (2005) studied this question.
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