Instantaneous optical modulation in bulk GaAs semiconductor microcavities

Picosecond pump-probe experiments at room temperature on a bulk GaAs microc avity are presented. The microcavity device is designed to adjust the cavit y mode energy 15 meV below the band gap energy of the intracavity bulk GaAs material. For low pump-energy densities (similar to muJ/cm(2)), ultrafast modulation of the reflectivity is demonstrated due to the purely coherent r efractive index change. A 5:1 contrast ratio is achieved and shows the pote ntial of the semiconductor microcavities for implementation in ultrafast al l optical switching. (C) 2001 American Institute of Physics.