Fabry-Pérot resonator

A Fabry-Pérot resonator is an optical device consisting of two parallel, highly reflective mirrors. Light enters the space between the mirrors, where it reflects back and forth multiple times. When certain wavelengths or colors of light match specific conditions, they interfere constructively, amplifying those wavelengths. This creates a narrow, sharp peak in the transmitted or reflected light spectrum, making the device useful for precise filtering, laser stabilization, and high-resolution spectroscopy. Essentially, it acts like a highly selective optical “filter” that allows only specific light wavelengths to pass or resonate within the cavity.