Photonics Dictionary

micro-ring resonator

A micro-ring resonator is a compact optical device that utilizes the resonant behavior of light within a small ring-shaped waveguide structure to selectively enhance or filter certain wavelengths of light. Micro-ring resonators are essential components in integrated photonics and are used in various applications, including optical communication systems, sensing, and signal processing.

Key features and principles of micro-ring resonators include:

Ring structure: A micro-ring resonator consists of a closed-loop, ring-shaped waveguide typically made of high refractive index materials, such as silicon or silicon nitride. Light circulates within the ring, forming resonant modes.

Resonant modes: When the circumference of the ring is an integer multiple of the wavelength of the light, constructive interference occurs, leading to the formation of resonant modes. These resonant modes result in enhanced optical effects at specific wavelengths.

Wavelength selectivity: The micro-ring resonator acts as a wavelength-selective filter or enhancer. It allows specific wavelengths of light that match the resonant conditions to be strongly coupled, while other wavelengths are less affected or experience destructive interference.

Coupling regions: Light is typically coupled into and out of the micro-ring resonator through coupling regions, which are waveguides that connect the ring to input and output ports. The coupling strength can be controlled to influence the resonator's performance.


Optical filters: Micro-ring resonators are used as narrowband optical filters in wavelength-division multiplexing (WDM) systems for optical communication.

Sensors: Changes in the refractive index of the material surrounding the micro-ring resonator can be detected through shifts in the resonant wavelength, making them useful for sensing applications.

Nonlinear optics: Micro-ring resonators can exhibit nonlinear optical effects, contributing to the development of compact optical signal processing devices.

Size and integration: Micro-ring resonators are particularly attractive for integrated photonics due to their small size and compatibility with semiconductor fabrication processes. They can be integrated with other optical components on a single chip.

Tuning capability: Some micro-ring resonators can be tuned by changing the effective refractive index or the geometry of the ring. This tunability allows for dynamic control of the resonant wavelengths.

Micro-ring resonators play a crucial role in the miniaturization and integration of optical devices, enabling advancements in optical communication, sensing technologies, and the development of compact and efficient photonics circuits.
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