Vertically Coupled Microring Resonator Filter for Integrated Add/Drop Node

The add/drop wavelength filter is an essential component in the new-generation photonic network. Microring resonator filters using high index contrast (HIC) optical waveguides are recently attracting attention as add/drop filters owing to their compactness, functionality such as dispersion compensation, and ease of filter synthesis. In particular, the vertically coupled microring resonator (VCMRR) filter is highly suited for the dense, large-scale integration of filter circuits. In this review, the fundamental characteristics advantageous to the add/drop filter nodes are introduced, and the recent progress in the development of vertically coupled microring resonator filters achieved mainly by the author’s group is described. key words: microresonators, integrated optics, optical waveguide filters, high index contrast optical waveguides, add/drop wavelength filters