In the traditional sense, the F-P cavity is composed of two parallel plates with a certain reflectivity, that is, a plane parallel cavity. At present, the commonly used scanning F-P cavity interferometer usually adopts a spherical mirror, which reduces the adjustment difficulty and improves the stability of the focal cavity structure system.
In a plane parallel cavity, the light parallel to the axis of the resonant cavity, after being reflected by a parallel plane mirror, still propagates parallel to the axis and will never escape from the cavity.
F-P cavity is the simplest optical cavity, which has the advantage of making full use of the working medium and making the beam oscillate in the whole working medium, and can be used for high-power output pulse lasers. In addition, the laser beam is not focused in the cavity, so it will not break down or damage the optical elements in the high-power laser.
However, this arrangement is rarely used for large lasers because it is difficult to align the F-P cavity. F-P cavity has large diffraction loss, high alignment accuracy and difficult assembly and adjustment. However, for the very short cavity with small mirror spacing, the loss caused by alignment is greatly reduced, so F-P cavity is often used in microchips, microcavity lasers and semiconductor lasers.