Microring resonator channel dropping filters

TLDR

Microring resonators coupled to waveguides enable compact, narrow‑band optical channel‑dropping filters with large free spectral range. The study aims to analyze these filters using a novel time‑domain mode‑coupling method. The response of filters comprising any number of resonators can be expressed as a continued fraction derived from the time‑domain mode‑coupling analysis. Coupling multiple rings yields higher‑order filters with better passband performance and greater out‑of‑band rejection, and the continued‑fraction method simplifies both analysis and synthesis.

Abstract

Microring resonators side coupled to signal waveguides provide compact, narrow band, and large free spectral range optical channel dropping filters. Higher order filters with improved passband characteristics and larger out-of-band signal rejection are realized through the coupling of multiple rings. The analysis of these devices is approached by the novel method of coupling of modes in time. The response of filters comprised of an arbitrarily large dumber of resonators may be written down by inspection, as a continued fraction. This approach simplifies both the analysis and filter synthesis aspects of these devices.