Optical Resonators and Filters

Dielectric optical resonators of small size are considered for densely-integrated optical components. High-index-contrast microresonators of low Q are shown, using microwave design principles, to permit wavelength-sized, low-loss, reflectionless waveguide bends and low-crosstalk waveguide crossings. The analysis and synthesis of high-Q, high-order microringand racetrack-resonator channel add/drop filters are reviewed, supplemented by simulation examples. Standing-wave, distributed Bragg resonator filters are also described. The study is unified by a coupled-mode theory approach. Rigorous numerical simulations are justified for the design of high-index-contrast optical “circuits”. Integratedoptical components are described within a polarization-diversity scheme that circumvents the inherent polarization dependence of high-index-contrast devices. Filters fabricated in academic and commercial research, and a review of microring resonator technology, advances and applications are presented.