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Scattering second harmonic ring could be observed in a bulk nonlinear medium with anomalous dispersion, whose generation is derived from complete phase matching of the incident light and the scattering light. By this specific phase matching under anomalous dispersion condition, we took advantage of total internal reflection, and realized high efficiency second harmonic output to gain a single pass conversion efficiency of up to 14.8% by only once reflection. It may suggest potential applications in micro-structures, such as micro cavities and waveguides.

We observed conical second-harmonic generation in a one-dimension anomalous-dispersion-like medium, which manifests itself as scattering-assisted nonlinear interaction via quasi-phase-matching sum frequency process. The parameters for the ring-shaped second harmonic beam are analyzed experimentally and theoretically, which disclose the structure information of the nonlinear photonic crystal and imply potential applications as characterization methods. Furthermore, by varying the angles of incident beam, the conical beam can be significantly enhanced owing to collinear nonlinear coupling between the input beam and the scattering light.