Critical comments are made on a recent paper by Bergstein and Schachter [J. Opt. Soc. Am. 54, 887 (1964)], which deals with the integral equations satisfied by the normal modes of laser resonators with plane-parallel end reflectors. It is pointed out that the paper lacks rigor, and that the numerical results do not agree very well with other published computations. The present state of knowledge relating to these integral equations is summarized.
S. P. MORGAN and T. LI, "Comments on “Resonant Modes of Optic Interferometric Cavities”," J. Opt. Soc. Am. 55, 1128-1132 (1965)