Diffraction Effects in a Resonant Cavity with Two Nonequivalent Apertures

Diffraction patterns and divergence of the fundamental mode of a laser are studied in the case of a plano-concave cavity with two-apertured mirrors. The effects of both apertures are shown to be nonequivalent. The sizes of their diameters control the geometry of the beam and, in particular, control the increase or the decrease of the divergence with respect to that of the nondiaphragmed cavity.