FabryPérotetaloner

A Fabry-Pérot etalon is an optical device consisting of two parallel, highly reflective surfaces separated by a precisely defined distance. This distance is often filled with a specific medium, such as air or a solid material. The etalon functions as a resonant cavity for light. When light enters the etalon, it undergoes multiple reflections between the two surfaces. Constructive interference occurs only for wavelengths that fit an integer number of half-wavelengths within the cavity.

This phenomenon leads to a wavelength-dependent transmission. Specifically, an etalon will transmit light most efficiently at wavelengths where the round trip path length within the cavity is an integer multiple of the wavelength. At all other wavelengths, destructive interference dominates, and the light is largely reflected. The spacing between the reflective surfaces and the reflectivity of these surfaces are critical parameters that determine the etalon's spectral resolution and the wavelengths of light it will transmit.

Fabry-Pérot etalons are widely used in spectroscopy for high-resolution wavelength selection and measurement. They are employed in applications such as laser tuning, spectral analysis of light sources, and as components in interferometers. The ability to precisely control the etalon's cavity length allows for fine-tuning of the transmitted wavelengths, making it a versatile tool in optical research and technology.