| In this work, a novel demultiplexer for optically time-division multiplexed (OTDM) fiber-optic communications is described. This demultiplexer, which is based on surface-emitted second-harmonic generation (SESHG) in optical waveguides, offers the unique advantage of recovering all multiplexed channels with one simple, integrated device, and exploits the relative ease of producing multilayer AlGaAs structures using epitaxial growth techniques. Resonant cavity enhancement (RCE) of the SESHG process has been investigated for the first time in the picosecond and femtosecond regimes, where the spectral content of the optical pulse is large compared to the resonance width of the cavity. A simple theory of RCE-SESHG has been developed and used to optimize the cavity parameters for operation with these short pulses. Furthermore, important limitations in GaAs-based SESHG waveguides have been identified and understood through simulation and experiment, and these limitations have been eliminated in new AlGaAs structures. The combination of resonant cavity enhancement and materials refinement has resulted in a factor of 23 improvement in the measured conversion efficiency, enabling the first-ever bit-error-rate measurements on an SESHG device. Error-free performance has been achieved at Gb/s data rates, demonstrating the viability of SESHG-based OTDM demultiplexing. |
