An optical resonator, the optical counterpart of an electronic resonant circuit, confines and stores light at certain resonance frequencies. It may be viewed as an optical transmission system incorporating feedback; light circulates or is repeatedly reflected within the system, without escaping. The simplest resonator comprises two parallel | Fundamentals of Photonics Bahaa E. A. Saleh Malvin Carl Teich Copyright 1991 John Wiley Sons Inc. ISBN 0-471-83965-5 Hardback 0-471-2-1374-8 E ronfc CHAPTER RESONATOR OPTICS PLANAR-MIRROR RESONATORS A. Resonator Modes B. The Resonator as a Spectrum Analyzer C. Two- and Three-Dimensional Resonators SPHERICAL-MIRROR RESONATORS A. Ray Confinement B. Gaussian Modes C. Resonance Frequencies D. Hermite - Gaussian Modes E. Finite Apertures and Diffraction Loss Charles Fabry 1867-1945 Alfred Perot 1863-1925 Fabry and Perot constructed an optical resonator for use as an interferometer. Now known as the Fabry-Perot etalon it is used extensively in lasers. 310 An optical resonator the optical counterpart of an electronic resonant circuit confines and stores light at certain resonance frequencies. It may be viewed as an optical transmission system incorporating feedback light circulates or is repeatedly reflected within the system without escaping. The simplest resonator comprises two parallel planar mirrors between which light is repeatedly reflected with little loss. Typical optical resonator configurations are depicted in Fig. . The frequency selectivity of an optical resonator makes it useful as an optical filter or spectrum analyzer. Its most important use however is as a container within which laser light is generated. The laser is an optical resonator containing a medium that amplifies light. The resonator determines the frequency and spatial distribution of the laser beam. Because resonators have the capability of storing energy they can also be used to generate pulses of laser energy. Lasers are discussed in Chap. 14 the material in this chapter is essential to their understanding. Several approaches are useful for describing the operation of an optical resonator The simplest approach is based on ray optics Chap. 1 . Optical rays are traced as they reflect within the resonator the geometrical conditions under which they remain confined are determined. .
