Research · Publication & note
Microring Resonators and Silicon Photonics
Review article
Abstract
Silicon Photonics is the technological to face the future challenges in data communications and processing. This technology follows the same paradigm as the technological revolution of the integrated circuit industry, that is, the miniaturization and the standardization. One of the most important building blocks in Silicon Photonics is the microresonator, a circular optical cavity, which enables many different passive and active optical functions. Here, we will describe the new physics of the intermodal coupling, which occurs when multi radial mode resonators are coupled to waveguides, and of the optical chaos, which develops in coupled sequence of resonators. In addition, an application of resonators in the label-free biosensing will be discussed.
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Research fields
Top-down
The work surveys silicon microring circuits fabricated for filtering, modulation, switching and coupled-resonator functions. It links the lithographic control of waveguide–ring gaps, radii and material stacks with the spectral response required by each device class.
Simulations & fits
Coupled-mode descriptions provide the common language for resonance linewidth, quality factor, extinction, dispersion and nonlinear detuning. The framework shows how the same compact resonator evolves from a passive filter into a dynamically controlled photonic element.
Characterization
Transmission, phase and power-dependent measurements are considered together because microring performance cannot be described by a resonance wavelength alone. Their combination separates coupling losses, intrinsic losses and thermally or carrier-induced changes in fabricated silicon devices.
RESEARCH TOPICS
CouplingThe review treats the bus waveguide as an active part of resonator physics, not only as an input and output. Its evanescent field sets radiative loading and can also mediate reactive coupling between radial families that share the same external channel. The resulting Fano or transparency-like line shapes depend on detuning, linewidth and coupling phase. At a larger scale, the article compares this intermodal interaction inside one ring with the collective response of sequences of side-coupled rings, where propagation phase connects distinct cavities.
MultimodeSilicon microrings support several radial families, each forming its own comb of azimuthal resonances. Their different field profiles give different Q values, waveguide overlaps and thermal responses. When two family members approach, treating them as independent Lorentzians fails: coherent interaction can suppress a narrow feature, invert a Fano asymmetry or produce an EIT-like window. The review uses these examples to show that multimode behaviour can be engineered for filtering and sensing rather than regarded only as unwanted spectral clutter.
NonlinearCirculating power enhances Kerr, free-carrier and thermo-optic effects, but their time scales and signs differ. A single ring can show bistability or self-pulsing; coupled cavities provide enough dynamical degrees of freedom for more complex and even chaotic behaviour. The review links these regimes to switching, optical memory and neuromorphic functions while stressing that a measured power-dependent shift is not automatically an ultrafast Kerr response. Correct interpretation requires separating instantaneous and delayed material mechanisms.
ResonatorsMicrorings are presented as compact silicon-photonic building blocks for wavelength filters, switches and label-free biosensors. Their usefulness follows from the combination of high Q, small mode volume and lithographic access, but each benefit increases sensitivity to roughness, absorption and fabrication detuning. By moving from a single resonance to radial-family coupling and then to resonator chains, the article explains how cavity geometry and network topology determine device behaviour more completely than Q alone.