In this thesis, we study silicon-based polygonal microdisk resonators with laterally coupled waveguides. We experimentally demonstrate the first waveguide-coupled octagonal microdisk channel add-drop filters. We also propose and demonstrate laterally waveguide-coupled round-cornered octagonal microdisk resonators with significantly improved add-drop filter characteristics from those of sharp-cornered octagonal microresonators. Octagonal microresonators belong to the class of polygonal microdisks that have the uniqueness of multiple pairs of flat sidewalls for lateral input- and output-coupling. It has been shown that waveguide-coupled polygonal microdisks exhibit much fewer coupled modes compared with waveguide-coupled circular microdisks of the same size. Our finite-difference time-dom...[ Read more ]

In this thesis, we study silicon-based polygonal microdisk resonators with laterally coupled waveguides. We experimentally demonstrate the first waveguide-coupled octagonal microdisk channel add-drop filters. We also propose and demonstrate laterally waveguide-coupled round-cornered octagonal microdisk resonators with significantly improved add-drop filter characteristics from those of sharp-cornered octagonal microresonators. Octagonal microresonators belong to the class of polygonal microdisks that have the uniqueness of multiple pairs of flat sidewalls for lateral input- and output-coupling. It has been shown that waveguide-coupled polygonal microdisks exhibit much fewer coupled modes compared with waveguide-coupled circular microdisks of the same size. Our finite-difference time-domain simulations and Fourier analysis of the simulated field patterns suggest that waveguide coupling to flat sidewalls in polygonal microresonators enable directional wavevectors, which are critical to the coupling of single or few resonance modes. Our experiments on silicon waveguide-coupled 50-μm-sized octagonal microresonators demonstrate only two dominant modes, with a Q of about 10⁴ and an extinction ratio of about 15 dB.

Integrating the silicon-based waveguide-coupled optical microresonators with metal-oxide-semiconductor (MOS) capacitors, we propose an accumulation-type electro-optic octagonal microresonator-based modulator. The principle is that lightwaves circulating in the microresonator and spatially overlapping with the selectively embedded MOS capacitor interface experience a phase shift due to the plasma dispersion effect, and thus result in a resonance blueshift. The simulations revealed a high-extinction-ratio, high-speed, and low-power modulation.

Using free-carrier-plasma-dispersion electro-optic effect in silicon, we experimentally demonstrate silicon microring carrier-injection-based modulators/switches with waveguide cross-coupling. The modulator extinction ratio can be tuned by forward-biasing either the microring or cross-coupled waveguide p-i-n diode, while modulating the other. We also demonstrate OR-logic switching functionality by simultaneously applying two different electrical data streams across the microring and cross-coupled waveguide diodes. Moreover, we analyze, fabricate and characterize silicon coupled-microring resonators-based electro-optic switching using injection-type p-i-n diodes.