We report on the observation of ultrafast (<1 ps) recovery of all-optical modulation based on below band gap, optically induced excess absorption using pump pulse energies of less than 4 pJ. At higher pump pulse energies, the hot carriers produced by two-photon absorption significantly reduce the recovery rate. The increase in absorption recovery times at the higher densities of hot carriers is consistent with a contribution to the nonlinear absorption change from hot electron assisted absorption. The measured hot electron assisted absorption cross section of 2×10−20 m2 is in good agreement with the theoretical value.
The refractive nonlinearities due to bandfilling and the plasma effect in a multiquantum well buried heterostructure semiconductor waveguide under reverse bias are probed using self-phase modulation techniques. Modeling of the self-phase modulation has allowed the magnitude of the phase modulation and nonlinearity recovery time constant to be extracted. π radians phase shift has been obtained for a coupled pulse energy of 32 pJ. The nonlinearity recovery time constant is 18±3 ps for an applied field of 34 MV m−1, limited by thermionic emission from the quantum wells.
Recent work on the development of integrated optical devices for nonlinear switching and processing has focused on the performance of Mach Zehnder1 and directional coupler2 switches. However previous research into optical fibres has identified the potential of the birefringent polarisation gate3 which is known to have better stability against external fluctuation than interferometric gates based on independent optical paths.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.