Ring resonator

A ring resonator is a waveguide closed into a loop that selectively enhances or filters a single, precisely defined wavelength of light circulating inside it under resonance conditions.

How does a ring resonator work?

When the loop's circumference is an exact multiple of the wavelength, light at that wavelength interferes constructively on every round trip, building up energy inside the ring and interacting strongly with the coupling waveguide. A ring with a circumference on the order of 10 micrometers filters a single wavelength out of a dense WDM spectrum, but is very sensitive to temperature changes, which in practice requires active thermal stabilization.

Applications

Ring resonators are used as WDM filters and multiplexers/demultiplexers, low-power modulators, and photonic sensors that detect changes in the surrounding refractive index.

Related terms

WDM

FDTD

PIC (Photonic Integrated Circuit)