Method for calculating the optical axis position in laser cavities

We present a method for calculating the optical axis contour in laser cavities using the geometric optics approximation. The deviation of the position of the optical axis in four-mirror nonplanar ring cavities is calculated for various cavity perturbations. Various types of laser cavities are considered and classified according to their symmetry. Deviations of the optical axis are determined in a nonplanar ring cavity that provides Kerr mode locking operation. A formula is given that relates the bend angle in four-mirror cavities to the angles of radiation incidence on the mirrors.