About cavities
Optical cavities are optical compo-nents in which light circulates in a very specific way. There are many different types of cavities for a wide range of applications.
I. Structure of optical cavities
Optical cavities consist of optical elements that allow the incident light to circulate on closed paths. In the simplest case, only two mirrors are required, which are held at a constant distance as possible by a so-called "spacer".
Depending on the application, lasers , frequency filters, high-precision frequency standards and frequency doublers can be implemented with such a cavity. In addition, cavities are main components of interferometric gravitational wave detectors, high-precision length meters, ring-down spectrometers, and many other applications.
II. Applications of Cavities
Laser
Lasers consist of an optical cavity in which the circulating light is generated by stimulated emission from an active medium. The geometry of the cavity largely determines the laser wavelength.
High-precision frequency standards
If the mirrors are held apart by a highly stable spacer, the laser wavelength (or frequency) can be stabilized to the length of this spacer. This allows for high-precision laser frequency standards with a relative stability of better than 99,999 999 999 999 9 %.
Second harmonic generation
Optical cavities with a nonlinear medium between the mirrors can be used to generate higher frequencies of light. These frequency-doubled lasers are used in laser pointers, high-power visible lasers, laser pulse measurement, and microscopy.
