Giant Excess Noise and Transient Gain in Misaligned Laser Cavities

The excess noise factor is calculated analytically for a very general class of optical cavities, and is shown to have a superexponential dependence on cavity misalignment, easily attaining values of order 10¹⁰. The physical basis is shown to be “transient gain” associated with amplified spontaneous emission. Similarly dramatic effects of symmetry breaking can be expected in other physical systems with non-normal modes.