Multi-frequency transverse properties of a Michelson mirror

Usually, the Michelson interferometer used as a selective mirror in a coupled-cavity laser is treated in the framework of plane waves although the laser beam has a finite lateral extent. We show that in general this approximation is not valid since the reflectivity of the Michelson mirror depends on the transverse profile of the input beam. This could allow for transverse mode selection in a laser without resorting to intracavity apertures. Single and multi-frequency cases are compared when the input is a TEM00 and a TEM10 Laguerre-Gauss beams.