Diffraction Loss and Selection of Modes in Maser Resonators with Circular Mirrors

Abstract

The losses, phase shifts and field distribution functions for the two lowest-order modes of interferometer-type maser resonators consisting of spherically curved mirrors with circular apertures are computed by solving a pair of integral equations numerically on a digital computer. Solutions are obtained for the symmetric geometry of identically curved mirrors and for the half-symmetric geometry consisting of one plane and one curved mirror, with the radius of curvature of the mirrors as a variable parameter. The confocal or near-confocal configuration is shown to have good mode-selective properties in that the ratio of the loss of the second lowest-order (TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf> ) mode to that of the lowest-order (TEM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</inf> ) mode is the largest of the configurations considered. The numerical results should be of interest to those concerned with the problem of mode selection in optical masers and with the design of single-mode masers with relatively low gain.