| This thesis presents experimental data on the optical performance of InGaAsP/InP active devices, including digital optical switches (DOSs) and bend-loss modulators, actuated by carrier injection as well as the electro-optical effect. It is demonstrated that carrier injection is a viable mechanism for optical switching in InGaAsP material, providing polarization and wavelength independent operation at response speeds on the order of nanoseconds.; Two mask layouts and several wafer layer structures were designed to study carrier injection and optimize performance of DOS devices. Using Mach-Zehnder and Fabry-Perot interferometer test structures, the relationship between refractive index modification and applied current density was characterized. It was determined that carrier lifetime and material bandgap play vital roles in determining switching contrast, switching speed, propagation loss, and driving power. The primary conclusion is that the switching speed is limited by Shockley-Reed-Hall carrier recombination times, and that increasing defect density reduces switching times at the expense of increasing required switching current. Alternatively, switching times may be reduced through over-driving. The dependence of refractive index modification on InGaAsP alloy was also studied, with the conclusion that a smaller bandgap material provides larger index changes at smaller current densities, with minimal detriment from absorption losses.; Several variations of the DOS device design were investigated, including devices with different waveguide width, branching angle, electrode shape, method of electrical isolation, and InGaAsP/InP heterostructure composition and doping. The optimized DOS devices demonstrated broadband operation, better than 25 dB contrast, less than 10 kA/cm2 switching current density, and an optical response time of less than 3 ns. Additionally, faster response was achieved by electro-optical actuation. This DOS design is a promising device for optical router configurations. They have been successfully cascaded in a crosspoint configuration to construct a 2x2 switch.; A bend loss attenuator actuated by carrier injection was also demonstrated, with significant improvements in performance over a straight waveguide attenuator. The device exhibits better than 15 dB modulation and <20 nanoseconds response time. The attenuator design is compact and can replace existing connection waveguides in a photonic integrated circuit, allowing it to be easily integrated. |
