title: Archimedean spiral cavity ring resonators in silicon as ultra-compact optical comb filters.
abstract: We present an ultra-compact comb filter using an add-drop ring resonator with an Archimedean spiral cavity. The cavity consists of two interleaved spiral branches which are connected in the center using arcs of circle of a radius that causes minimum bend loss. We describe the design procedure and examine the physical parameters governing the resonator performance. As an example, we demonstrate experimentally a comb filter with a 25 GHz channel spacing made of silicon photonic wires and only occupies an area of 80 x 90 microm(2), approximately a 70 fold size reduction compared to a racetrack resonator. The filter transmission is free of spurious reflections, attesting to the smooth transition between different sections of the resonator cavity. Over a 40 channel wavelength span, the filter exhibits a quality factor Q > 35,000, extinction ratios > 10 dB, and an excellent power uniformity with variations < 0.5 dB for both the through and drop ports.
authors.affiliation: Institute for Microstructual Sciences, National Research Council Canada, 1200 Montreal Road, Ottawa, Canada.
authors.forename: Dan-Xia
authors.initials: DX
authors.lastname: Xu
authors.forename: André
authors.initials: A
authors.lastname: Delâge
authors.forename: Ross
authors.initials: R
authors.lastname: McKinnon
authors.forename: Martin
authors.initials: M
authors.lastname: Vachon
authors.forename: Rubin
authors.initials: R
authors.lastname: Ma
authors.forename: Jean
authors.initials: J
authors.lastname: Lapointe
authors.forename: Adam
authors.initials: A
authors.lastname: Densmore
authors.forename: Pavel
authors.initials: P
authors.lastname: Cheben
authors.forename: Siegfried
authors.initials: S
authors.lastname: Janz
authors.forename: Jens H
authors.initials: JH
authors.lastname: Schmid