Resonant optical interactions in active dielectric films

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Abstract
An investigation of oblique plane-wave electromagnetic scattering in active dielectric films reveals the existence of anomalously large resonances that occur at discrete plane-wave angles of incidence. These resonances may be understood from a ‘‘leaky wave’’ phase matching condition whose predictions for the first three modes agree to within a few percent of those obtained from a rigorous treatment using Maxwell’s equations. Experiments using finite-diameter pump and probe laser beams verify the existence of these scattering resonances with enhancements of the scattered field intensities on the order of 100 observed in active dielectric films as thin as 6 μm. Saturation effects are discussed in the context of a very simple model whose predictions agree qualitatively with experimental measurements. Two novel laser oscillator configurations based upon resonant leaky waveguide interactions were tested and found to have very high-energy extraction efficiency (≥18%) with oscillation being easily achieved using active dielectric films as thin as 6 μm.