Degenerate Optical Cavities. II: Effect of Misalignments.

A simple expression is given for the response of degenerate cavities suffering from arbitrary misalignments, and numerical results are presented. The method of resonance excitation is carried out analytically with the help of a complex ray representation of gaussian beams. It is first shown that the modulus and phase of such complex rays can be identified with, respectively, the beam radius and the phase of the on-axis field. This identification simplifies the calculation of the coupling factor between two gaussian beams, which is needed in deriving the expression for the response. For the case of conventional cavities, the results are in exact agreement with results derived from the Laguerre-Gauss or Hermite-Gauss mode theory. The case of degenerate cavities with large and possibly nonorthogonal misalignments, of interest in various nonresonant multipath systems, is also discussed.