Optical resonators with variable reflectivity mirrors

In this paper we investigate circular optical resonators with gaussian profiles of the mirror reflectivities. Closed form solution to the integral equations for such resonators are obtained. The dominant TEM o,o mode characteristics of a resonator consisting of one variable reflectivity mirror (VRM) and one uniform reflectivity mirror (URM) are considered in detail for a variety of parameters. This resonator is particularly suitable for high-gain lasers. Its advantages in comparison to the conventional type are: (i) there is larger mode volume utilization, and (ii) the power transmitted at the variable reflectivity mirror can in principle be utilized as the power output. We discuss dependence of the spot sizes on laser gain and mirror-curvature tolerances and present a specific design of a Fabry-Perot resonator for fundamental mode operation and the expected performance.