Abstract
This research includes simulation, fabrication and measurement for silicon-based modulators through free-carrier plasma dispersion effect. By taking advantage of this plasma dispersion effect, a Mach-Zehnder-Interferometer (MZI) structure was employed and successfully demonstrated signal modulation with speed more than 100 MHz, which is only limited by the experimental instrument. Regarding the research work, a rib silicon waveguide was fabricated by standard CMOS process on silicon-on-insulator(SOI) wafer. The propagation loss and the coupling loss of rib waveguides were measured to be 15.52dB/cm and 17.37dB per Coupler, respectively. Multimode interference(MMI) couplers were used to split and combine light in the MZI configuration. To introduce a significant phase shift, a 5V bias was applied on one arm of the MZI branch, which was realized by incorporating a p-n junction on the rib waveguide. Experimental results show that the operational speed can exceed 100 MHz while the insertion loss was relatively high (about 64 dB). The extra loss is due to unintentional high dose of impurity on the waveguide region. A future work includes a better control on the doping level and reduction of surface roughness on the rib waveguide.