Applied optics
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Conical ring emission from a short-cavity dye laser has been observed and modeled as Kastler rings, that is, the high-angle emission modes of a plano-plano (Fabry-Perot) laser cavity in agreement with the predictions made 31 years ago by Kastler [Appl. Opt. 1, 17 (1962)]. The excitation of the discrete rings is due to a transfer of energy from the axial modes rather than to spontaneous emission. The mechanism for energy transfer is argued to be scattering of light from imperfections on the mirror surfaces.