tvåspegelresonator

A two-mirror resonator, also known as a Fabry-Pérot resonator or simply an optical cavity, is a fundamental optical element consisting of two parallel mirrors separated by a certain distance. These mirrors are typically highly reflective at the desired wavelength of light. When light enters the resonator, it undergoes multiple reflections between the mirrors. This repeated reflection process creates a standing wave pattern within the cavity if the distance between the mirrors is an integer multiple of half the wavelength of the light.

The key characteristic of a two-mirror resonator is its ability to resonate at specific wavelengths. Only light whose wavelength satisfies the resonant condition can build up intensity within the cavity. This is because constructive interference occurs for these wavelengths after multiple reflections, leading to a significant amplification of the light. Other wavelengths experience destructive interference and are quickly suppressed.

Two-mirror resonators are widely used in various optical applications. They form the basis of many lasers, where the gain medium is placed inside the resonator to amplify light at the resonant frequencies. They are also employed in optical filters, where they selectively transmit or reflect certain wavelengths. In spectroscopy, they can be used to enhance the interaction of light with a sample, leading to more sensitive measurements. The precise spacing and reflectivity of the mirrors are crucial parameters that determine the resonator's resonant frequencies and its quality factor, which quantifies how sharp the resonant peaks are.