Far-Infrared Light Generation at Semiconductor Surfaces and its Spectroscopic Applications

Femtosecond pulses of far-infrared (FIR) radiation can be generated in the depletion field near semiconductor surfaces under optical excitation via the inverse Franz-Keldysh effect or electric-field-induced optical rectification. This coherent mechanism differs from previously proposed incoherent mechanisms and is expected to dominate for nonresonant excitation as well as for resonant excitation with optical fields. Two femtosecond time-resolved spectroscopic applications using a visible excitation pulse and a FIR probe pulse are described