Linear three-mirror resonator

A theory of a three-mirror resonator is based on the concept of traveling waves and it is developed by applying a matrix calculation method. The important parameters of the resonator are determined and analytic solutions depending on these parameters are obtained for the mutually related resonator characteristics, such as the threshold gain, natural frequencies, amplitude ratios, and differences between the phases of traveling waves in different sections of the resonator. The condition of mutual symmetry is established for modes of two types that can exist in a three-mirror resonator. A criterion is derived for distinguishing resonators in accordance with the nature of the behavior of modes of two types as a function of the difference between the lengths of the sections. The main theoretical predictions are checked against the results of several experiments carried out on a helium–neon laser.