ABSTRACT
Mode analysis of unstable resonators with variable reflectivity mirrors of various shape was developed by Kumagai et al, Anan’ev and Sherstobitov, Sherstobitov and Vinokurov, and by McAllister et al through the numerical or asymptopic solution of the resonator equations. Although the advantages of unstable resonators employing mirrors with Gaussian reflectivity profiles have been recognized for many years, only a few practical devices with quasi-gaussian shape have been successfully developed. The cavity modes resulting from the application of supergaussian mirrors to unstable resonators also present supergaussian mirrors to unstable resonators also present supergaussian profiles, which are bell–shaped and considerably flatter in the centre than a Gaussian curve. The simplest approach to an analytical treatment of resonators with variable reflectivity mirrors is to consider Gaussian tapering of the reflectivity. For unstable resonators with supergaussian mirrors the geometrical optics provides for a satisfactory approximation of mode profiles and losses.
