Dynamic Band Unblocking And Leakage Two-Photon Absorption In Insb

An experimental demonstration of a dynamic decrease of the optical band gap of bulk n-InSb induced by picosecond, midinfrared laser pulses is reported. This occurs as a result of laser heating of the quiescent electron distribution by free-carrier absorption. The hot electrons vacate low-energy states near the conduction;band minimum,unblocking terminal states for two-photon absorption across the band gap. This \u27\u27leakage\u27\u27 two-photon absorption is detected as a consequence of changes to 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