Abstract

The temperature dependence of two-photon absorption (2PA) in InSb has been studied with CO₂ lasers for many years.¹ When this semiconductor is cooled to <20 K, the optical absorption edge increases so that 2PA is just out of resonance with 10.6 μm laser light (2ħω< E_g). This is due to a combination of bandgap expansion at low lattice temperature and band- blocking by conduction electrons. In a series of experiments we show that intense, picosecond CO₂ laser pulses can remove band-blocking, turning on “leakage" 2PA.

© 1996 Optical Society of America