Generation of subpicosecond infrared laser pulses produced by optical switching from low temperature grown gallium arsenide

Pico/femtosecond optical semiconductor switching using both a reflection and. a transmission switch for 10.6 μm has been used before to produce pulses as short as 130 fs. However, for many experiments, for example those involving intracavity switching, it is desirable to operate with a single reflection switch. To this end we investigated many semiconductor surface structures. In this talk we discuss the fastest and most reliable structure investigated which is capable of generating 10 μm pulses shorter than 500 fs. The CO₂ -laser pulse is created by reflection from a transient metallic-like semiconductor plasma. The speed of this switching technique relies on the ultra short carrier lifetime (⩽0.5ps) in low temperature molecular beam epitaxy (MBE) grown GaAs (LT-GaAs). Subpicosecond recombination time is achieved through the introduction of high density As-recombination centers during the growth of GaAs. Our experiments show that LT-GaAs, grown under the following conditions is ideally suited for optical semiconductor switching of below band gap IR radiation