DYNAMIC BAND UNBLOCKING AND LEAKAGE 2-PHOTON ABSORPTION IN INSB

An experimental demonstration of a dynamic decrease of the optical ban d gap of bulk n-InSb induced by picosecond, midinfrared laser pulses i s reported. This occurs as a result of laser heating of the quiescent electron distribution by free-carrier absorption. The hot electrons va cate low-energy states near the conduction;band minimum,unblocking ter minal states for two-photon absorption across the band gap. This ''lea kage'' two-photon absorption is detected as a consequence of changes t o the refractive index and absorption coefficient of the semiconductor caused by photocarriers. The onset of dynamic band unblocking agrees with a calculation of laser-induced electron heating.