Transverse modes, waveguide dispersion, and 30 ps recovery in submicron GaAs/AlAs microresonators

We have studied room-temperature optical gating of ∼5 ps pulses in GaAs/AlAs microresonators with diameters ranging from 0.5 μm to 1.5 μm by using a high-refractive-index lens system having a numerical aperture of 1.3. The larger devices exhibited well-defined transverse modes, which caused decreased modulation of the probe beam. Waveguide dispersion, present in all the devices, showed fair agreement with calculations. The smallest diameter devices (0.5 μm) show high modulation, fully recover in 30 ps, and have their peak transmission wavelengths shifted by 500 Å compared to a large ∼10 μm nearby region.