Abstract

The effect of charge recombination, after exciton saturation, in a strained InGaAs/InP MQW sample has been analyzed. The pump-and-probe measurement is obtained through a Mach–Zehnder configuration supplied by an FCL laser mode-locked at 76 MHz and producing 8 ps (FWHM) pulses. A calibration delay is inserted in the pump branch, while a high resolution double delay line is located in the probe arm. Through the recombination beam-splitter pump and probe beams are translated and focused onto the sample, where they intersect. The two beams are linearly and orthogonally polarized to avoid the interference due to the diffraction grating formed in the sample when the pump and probe paths are balanced. Particular care has been devoted to obtaining a stable probe spot with respect to the pump on the MQW during the scanning of the double delay line. From the transmittivity curves vs. pump–probe delay, the time constant of the exciton saturation decay has been evaluated. Work is in progress to lower the time constant of the charge recombination effect exploiting two transverse electric fields applied to the structure, which should become suitable for realizing optical switching devices.

© 1992 Optical Society of America