We report an experimental observation of optical second-harmonic generation in an amorphous silicon–nitride based planar microcavity. The spectral dependence of the second-harmonic signal is investigated as a function of both wavelength and polarization state of the fundamental beam. The second-harmonic signal is enhanced by two orders of magnitude at the Fabry–Perot resonance. We ascribe the origin of the optical nonlinearity to surface second-harmonic generation occurring at the interfaces of the multilayered structure, where the resonant enhancement is due to the high intracavity fundamental light intensity and to the increase of the photonic density of states. Analysis of polarization dependence shows that interfacial second-order nonlinearity results from a distribution of dipoles directed perpendicularly to the plane of the film and distributed accordingly to an ∞mm point group symmetry.

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We report on the realization of microcavities made of hydrogenated amorphous-Si 1−x N x multilayers, with dual-wavelength periodic dielectric mirrors in order to obtain first and second order stop bands. Optical second-harmonic generation with simultaneous resonance for the pump and harmonic waves is demonstrated at finite values of the angle of incidence. The results are in good agreement with a theoretical calculation of the harmonic generation process based on a nonlinear polarization localized at the interfaces between different amorphous layers.

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