Generation of 1-ps infrared pulses at 10.6 microm by use of low-temperature-grown GaAs as an optical semiconductor switch.

Using a GaAs layer grown by molecular-beam epitaxy at low substrate temperature as an optical semiconductor switch, we demonstrate the generation of picosecond infrared pulses at 10.6 microm. To our knowledge, this is the first time that ultrashort pulses have been generated by use of only one reflective switch. A cross-correlation method, which is used to measure the pulse width, indicates that the pulse width is ~1 ps. A 200-nm-thick, low-temperature molecular-beam-epitaxy-grown GaAs layer, acting as an ultrafast active switching element, was grown at a low temperature of 320 degrees C on a GaAs substrate and annealed at 550 degrees C. The presence of a high density of As precipitates in this material that act as fast recombination centers gives the optically injected carriers in low-temperature molecular-beam-epitaxy-grown GaAs a lifetime of 0.5 ps. We also discuss the feasibility of the extension of this technique to other mid- and far-infrared lasers.