We have previously discussed the transmission and coupling losses of a Gaussian beam in a folded waveguide structure made of two hollow square waveguides placed symmetrically above a spherical mirror with a nonzero on-axis angle between. Here we investigate the additional loss due to the misalignment of the mirror (axial displacement and/or angular tilt). The theoretical results are in good agreement with experiment and provide alignment tolerances for folded waveguide design.
J. Banerji, A. R. Davies, R. W. J. Devereux, C. A. Hill, and R. M. Jenkins, "Effects of curved mirror misalignment in a folded waveguide," Appl. Opt. 29, 777-785 (1990)