Amplitude–phase mode structure of an astigmatic Gaussian beam in ring lasers with a nonplanar four-mirror cavity and an aperture

The structure of the fundamental mode field in a nonplanar ring four-mirror resonator with an aperture is determined taking into account rotations of the amplitude and phase distributions of an astigmatic Gaussian beam. The rotation angles of the axes of these distributions are calculated upon variations in the characteristic aperture size and the angle of curvature (nonplanarity) of the resonator. The effect of the resonator aperture and nonplanarity on the intensity distribution of the interference pattern behind a mixer is studied. It is shown that interference fringes have a slope depending on the orientations of the amplitude and phase distributions of the mode.