High Speed Low Power Nonlinear Optical Signal Processing

摘要

During the two-year period of this contract, substantial progress was made in the understanding of both the linear and the nonlinear optical properties of direct gap semiconductors and in the implications for high speed, low power, nonlinear optical signal processing. In particular, the detuning and the temperature dependence of the damping of an exciton-polariton was obtained for the first time. The lowest single beam switching energy (< 4 pJ) and the fastest reported ON/OFF switching (< 1 ns) bistable device with clearly resolved stable states was demonstrated using the nonlinearity associated with bound excitons in CdS. Thermal effects on the millisecond and microsecond time scales were experimentally studied. Optical bistability due to induced absorption near the free and bound exciton was experimentally studied with and without a Fabry-Perot cavity. Large degenerate four-wave mixing signals were observed near free and bound excitons in CdS at cryogenic temperatures. Nonlinear transmission signals were studied at different detunings below the free exciton resonance and at temperatures up to 120 K. These signals were interpreted in terms of a broadening of the free exciton resonance by exciton-exciton collisions. The quantum confined stark shifting of a quantum dot was performed for the first time. A new generation of efficient optical modulators is envisioned. (Author)