Bragg-induced orbital angular-momentum mixing in paraxial high-finesse cavities

Abstract

Numerical calculation of vector electromagnetic modes of plano-concave microcavities reveals that the polarization-dependent reflectivity of a flat Bragg mirror can lead to unexpected cavity field distributions for nominally paraxial modes. Even in a rotationally symmetric resonator, certain pairs of orbital angular momenta are necessarily mixed in an excitation-independent way to form doublets. A characteristic mixing angle is identified, which even in the paraxial limit can be designed to have large values. This correction to Gaussian theory is zeroth-order in deviations from paraxiality. We discuss the resulting nonuniform polarization fields. Observation will require small cavities with sufficiently high Q. Possible applications are proposed.

Corrected typos in Fig. 2 and text. Added Journal Ref. For higher-quality figures, see http://darkwing.uoregon.edu/~noeckel/papers.php#xref30