fp cavity working principle

The F-P cavity is a passive optical resonant cavity, first produced in 1897, invented by the French Charles Fabry and Alfred Perot***, and is now widely used in optical communications, lasers, and spectroscopy to control or measure the wavelength of light.

Traditionally, an F-P cavity is composed of two parallel flat plates with a certain reflectivity, i.e., a plane-parallel cavity. Currently used scanning F-P cavity interferometers, on the other hand, usually use spherical mirrors to **** focal cavity structure to reduce the difficulty of adjustment and improve system stability.

In a plane-parallel cavity, a ray of light parallel to the axis of the resonance cavity is reflected by a parallel plane mirror, and the direction of propagation is still parallel to the axis, and will never escape from the cavity.

The F-P cavity is the simplest optical cavity, and has the advantage of making full use of the working material, so that the beam oscillates throughout the working material, which can be used for high-power output pulsed lasers. In addition, the laser beam is not focused inside the cavity and will not break through or damage the optics in high power lasers.

However, this arrangement is rarely used in large lasers due to the difficulty of aligning the F-P cavity, which has high diffraction losses, high alignment accuracy requirements, and mounting difficulties. However, for very short cavities with small mirror spacing distances, the loss due to alignment is greatly reduced, so F-P cavities are commonly used in microchip and microcavity lasers, semiconductor lasers