Date of Award

January 2016

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering

First Advisor

Minghao Qi

Committee Member 1

Vladimir Shalaev

Committee Member 2

Xianfan Xu

Committee Member 3

Yi Xuan


The potential of on-chip photonics is limited by the difficulty in coupling light from optical fibers to on-chip waveguides. Specifically, 3rd-order nonlinear on-chip photonics usually requires high optical power. Hence the first major focus of this research is to design high-efficiency edge couplers. To achieve this goal, loss mechanisms of basic inverse taper couplers are analyzed and experimentally verified. Then a cantilever-encapsulated inverse taper is demonstrated to further lower coupling loss compared to basic inverse tapers. Nonetheless, both couplers are designed to couple with lensed fibers. Hence for flat fibers with larger mode-field-diameter (MFD), a novel sub-wavelength grating based edge coupler is proposed and experimentally demonstrated to have 1.9dB/facet loss. Eventually a silicon multi-section taper with intermediate SU-8 waveguide cladding is proposed for flat fibers with even larger MFD and experimentally verified. Based on the result several suggestions are proposed for further improvement.