resonator

A resonator is a device or structure that naturally tends to oscillate at particular frequencies, known as its resonant frequencies, when excited. In a resonator, energy transfers cyclically between different forms (for example, kinetic and potential energy in a mechanical system or electric and magnetic energy in an electrical circuit), and the oscillation persists for a time limited by damping. The geometry, boundaries, and material properties determine the resonant modes and frequencies.

Resonators are categorized by their primary energy storage mechanism. Mechanical resonators include masses connected by springs or vibrating bodies such as tuning forks. Acoustic resonators rely on standing sound waves in air or other media, such as air columns in pipes or Helmholtz cavities found in musical instruments. Electrical resonators use reactive components like inductors and capacitors (LC circuits) or piezoelectric elements such as quartz crystals to store energy and define a resonant frequency. Optical resonators store light in cavities formed by mirrors or waveguides, with laser cavities and ring resonators serving as key examples.

Important properties include the resonant frequency, the mode shape, and the quality factor Q, which measures how long energy remains in the system relative to the oscillation period. Higher Q indicates narrower bandwidth and lower damping.

Applications span timing, filtering, sensing, and signal generation: quartz crystal clocks, RF filters, MEMS sensors, musical instruments, and laser systems. Resonators are also used to control bandwidth in communications and to study wave phenomena in physics.