Optimization of plasma dispersion modulators in silicon-on-insulator.

摘要

This thesis presents an investigation of the causes of and design factors affecting power consumption within SOI-based plasma dispersion optoelectronic devices. We also consider the issue of thermal buildup, one of the few such investigations ever performed. We examine the effects of several novel design improvements upon three prototypical devices: a Mach-Zehnder interferometer (MZI), an electroabsorption modulator and a 2 x 2 GMZI switch.;Measurements of twenty-six fabricated Mach-Zehnder interferometers showed a typical operating current of 35 mA and attenuation of 8 dB with a bandwidth of ∼1 MHz. Comparison of the various fabricated devices confirms at a statistically meaninful level that the design modifications improve modulator performance. Numerical simulation, inferences from optical measurements and direct thermal imaging cap the maximum rise in operating temperature of the devices at 0.02 K. Performance of the electroabsorption modulators were found to be lower because of the increased injected carrier density required for operation. A maximum attenuation of 13 dB at a current of 50 mA was recorded.;Fabrication difficulties led to 2 x 2 GMZI switches that functioned through thermal rather than electrical processes. Average extinction ratios and crosstalks were measured to be 5.6 dB and 3 dB, respectively. Switching power was measured to be as low as 180 mW, one of the best reported for an SOI-based switch.;We find that both power consumption and thermal buildup within plasma dispersion devices is dominated by carrier recombination within the heavily doped emitter contacts. Numerical simulations indicate that this contribution can be reduced by an order of magnitude through the use of heavily doped polysilicon emitters. A further order of magnitude improvement is possible through the use of a novel "pinhole" contact structure, which replaces the traditional strip contact architecture used in all previously reported optoelectronic devices.