Summer 2010 Intern Project- Nicolas Julian

POLARIZATION CONTROL IN INTEGRATED SILICON OPTOELECTRONICS

Nicholas Julian
Electrical & Computer Engineering
UC Santa Barbara

Mentors: Daoxin Dai and Zhi Wang
Faculty Advisor: John Bowers
Department: Electrical & Computer Engineering

Integrating optoelectronic devices on the hybrid Silicon/III-V platform has the potential to simultaneously conserve energy and increase computing ability. A key feature of the electromagnetic fields within an optoelectronic device is its polarization. The behavior of transverse-electric (TE) and transverse-magnetic (TM) polarized fields within planar integrated optical devices differ significantly, resulting in negative effects such as cross-talk when both polarizations are simultaneously present. Thus, polarization controlling devices such as polarization beam splitters (PBS's) and polarizers are desirable for integrated Silicon optoelectronics. Polarizers filter out light with an undesired polarization state to avoid crosstalk, and PBS's can be used for either separating or combining transverse-electric (TE) and transverse-magnetic (TM) polarized light, which is also useful for polarization (de)multiplexing systems. For our contribution, we will experimentally characterize silicon-on-insulator (SOI) based polarizers and PBS’s. The PBS design is based on the structure of a directional coupler, in which the coupling length of TE polarization is designed to be 1/4 of that of TM polarization. The polarizer is based on a shallowly-etched ridge waveguide, in which the TM polarization has much higher loss than the TE polarization. In order to characterize the fabricated polarizer and PBS, several measurement approaches are developed and compared. An appropriate test bench and procedure is finally given. With the appropriate test bench, polarizers and PBS's with varying design parameters are characterized and analyzed.

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