Using a conventional microwave photonic technique, we demonstrate lightwave switching in laterally coupled GaAs-AlGaAs microring resonators by free carrier injection. The ring waveguide is optically pumped just above its bandgap energy, which results in a temporal tuning of the microring resonant wavelengths by the refractive index change due to the induced free carriers. Both the transmission and the phase function of the resonators are investigated and used to demonstrate all-optical switching. The switching time, limited by surface recombination of carriers, is 20 ps. A switching energy of a few picojoules shifts the microring resonance by 1.2 nm.
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