SUBNANOSECOND REFLECTIVITY MODULATION KINETICS IN GAAS GAALAS MICROCAVITIES/

We study the subnanosecond reflectivity kinetics of distributed Fabry- Perot cavities composed of two GaAs/AlAs Bragg reflectors enclosing a central GaAs layer. The structure reflectivity exhibits a sharp minimu m in the absorption edge of GaAs at the temperature of 300 K, around t he wavelength of 885 nm. The photogeneration of an electron-hole plasm a causes a shift of the cavity resonance. The switch energy and the re covery time are investigated. Switching capabilities are observed with excitation energies of few tens of mu J/cm(2). We correlate the refle ctivity kinetics to the plasma dynamics in the central GaAs zone of th e structure, especially to the density and temperature relaxation.