Picosecond pump–probe experiments at room temperature on a bulk GaAs microcavity are presented. The microcavity device is designed to adjust the cavity mode energy 15 meV below the band gap energy of the intracavity bulk GaAs material. For low pump-energy densities (∼μJ/cm2), ultrafast modulation of the reflectivity is demonstrated due to the purely coherent refractive index change. A 5:1 contrast ratio is achieved and shows the potential of the semiconductor microcavities for implementation in ultrafast all optical switching.
We propose a modeling of the microcavity-coupled optical Stark effect that we compare to degenerate pump-probe experimental results obtained at room temperature on a bulk GaAs microcavity. The cavity energy mode is adjusted 15 meV below the edge of the GaAs bandgap. With a pump intensity as low as 0.4 MW/cm2, we could demonstrate an instantaneous reflectivity modulation with a 5:1 contrast ratio. The good agreement between experiment and modeling is promising to design structures well suited to all-optical modulation with low switching intensities.
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