Ultrafast optical nonlinearity of low-temperature-grown GaInAs/AlInAs quantum wells at wavelengths around 1.55 μm

The ultrafast optical response of low-temperature-grown GaInAs/AlInAs multiple quantum wells is studied in pump-probe experiments with a femtosecond Er:fiber laser. As-grown samples doped with beryllium (concentration of 8x10(17) cm(-3)) display a nonlinear transmission change, which decays by carrier trapping with a time constant of 230 fs. Experiments with pairs of ultrashort pulses separated by 1.5 ps demonstrate a fast modulation of transmission and very small accumulation effects, making this material highly promising for all-optical switching. Substantially longer recovery times are found in annealed, Be-doped samples and in undoped samples. (C) 2002 American Institute of Physics.