Effect of Mirror Rims on Modes and Losses of a Planar Fabry-Perot Resonator

Abstract

A theoretical investigation is presented on modes and losses of an open resonator terminated by plane mirrors with rims along the edges. Three different shapes are examined: namely, step, sloped, and curved rims. The appropriate integral equation has been solved with the iterative procedure by computer for some low order modes. The losses exhibit an oscillating trend when the rim height varies. For some values of the Fresnel number and of the ratio between the rim width and the mirror semi-aperture, some mode crossings and/or mode inversions have been observed. When suitable rim dimensions are chosen, the losses are noticeably reduced with negligible variations of the field inside the resonator and hence of the mode volume.