Using Backscattering and Backcoupling in Silicon Ring Resonators as a New Degree of Design Freedom

Abstract

Silicon optical ring resonators are potentially valuable for many applications. Due to the limited design freedom (coupling coefficient and roundtrip length), the functionality and performance cannot always be fully explored and optimized. In addition, high-contrast silicon ring resonators suffer from parasitic coupling between their clockwise and counterclockwise modes as well as parasitic coupling from the input to both circulating modes, which degrades or even distorts the response. Herein, an overview is given to harness these effects as additional design parameters to overcome the detrimental effects and realize novel functionalities in silicon ring resonators. Through simulations and experimental characterization, it is shown how the manipulation of backreflection and backcoupling enables various novel functions, including tunable Fano resonances with maximum slope rate over 700 dB nm−1 , tunable electromagnetically induced transparency, which slows light down over 1100 ps, a single-mode silicon ring resonator with a free spectral range over 150 nm and tuning efficiency over 11 times higher compared to that of conventional silicon ring resonators, fundamental suppression of inevitable backscattering, spectral tuning, single sideband filtering, and ultrahigh Q/large finesse resonances.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Steering Directional Light Emission and Mode Chirality through Postshaping of Cavity Geometry

“…We envision that the steered optical devices acquiring exotic properties will potentially open up new concepts and possibilities in light sources, sensors, and photonic integrated circuits. [50]…”

Fano Resonance in Artificial Photonic Molecules

“…The coupled mode theory promises insight into modes interactions in time, and can accurately describe the fascinating electromagnetic oscillation in photonic molecules. [ 37,38,83,86,103–107,124–126 ]…”

“…[ 38,127–131 ] Typical optical microcavities used for Fano resonance realization include whispering‐gallery‐mode, plasmonic, Fabry–Pérot (FP), and photonic crystal cavities. [ 37,38,83,114 ] Assembling optical cavities in a wide range of structures, various artificial photonic molecules configurations have enabled the Fano resonance and brought forth the development of highly integrated photonic circuit.…”

“…The Fano line shape profiles are related to the system's structural parameters and the electromagnetic parameters of ambient media. So, various systems, including optical cavities, [ 36–39 ] nanoclusters, [ 40–43 ] photonic crystals, [ 44–45 ] gratings, [ 46–49 ] metamaterials, [ 50–53 ] metasurfaces, [ 54–57 ] and many others, [ 58–63 ] have been proposed theoretically and observed experimentally to exhibit Fano resonance. Inspired by recent progress in numerous novel materials, [ 64–69 ] including 2D materials with exotic optoelectronic properties, [ 70–72 ] superconducting materials, [ 73,74 ] phase‐changed materials, [ 75,76 ] low loss dielectric materials [ 77,78 ] and quantum dots, [ 79–82 ] many opportunities to investigate Fano resonance are anticipated.…”

Topological phases in ring resonators: recent progress and future prospects

“…For further in-depth discussion of the physics and applications of photonic ring resonators, we recommend the articles by Bogaerts et al [12], Morichetti et al [55], and Li and Bogaerts [65].…”