Optically controlled transmission of InGaAsP epilayers

We investigate the transmission of InGaAsP epilayers lattice matched to InP substrates under optical excitation at normal incidence to the surface. Near the gap wavelength (lambda = 1.3 microm) we observe a transmission change of 20% for a 0.5-mW pump beam at a wavelength lambda(2) = 790 nm. Switching dynamics are shown to be limited by carrier lifetimes of tau approximately 2 nsec. A simple analysis based on parabolic bands and direct electronic transitions provides a good description of the experiments.