ABSTRACT
Microring resonators have many merits, compared with other kinds of resonators. First, mirrors or gratings are not needed to get optical feedback; thus, microring resonators are not so hard to fabricate and are very suitable for on-chip optical integration. Second, the microring resonator is a traveling-wave resonator. Third, multiple microring resonators can be coupled in series or parallel to achieve a box-like response and a large free-spectrum range. Nowadays, as a basic component, the microring resonator has been widely employed to construct various optical devices, such as filters, modulators, switches, logic gates, delay lines, and sensors. Microring resonators can construct various functional devices with other optical components, for which transfer functions can be obtained using the transfer matrix method. First, the readers divide the complicated configuration into basic elements, such as directional coupler, transmission line, and microring resonator. Then, with their transfer matrixes employed, the transfer function for the aimed configuration can be derived.
