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Third-harmonic generation in silica wedge resonators
preprintposted on 2023-01-10, 03:29 authored by Jorge H. Soares, Laís Fujii Dos Santos, Felipe G. S. Santos, Marvyn Inga, Yovanny A. V. Espinel, Gustavo S. Wiederhecker, Thiago P. Mayer Alegre
Whispering-gallery-mode microcavities are known to have high optical quality factor, making them suitable for nonlinear optical interactions. Here, third-harmonic generation is observed using a relatively small radius wedge silicon oxide optical microcavity. The small radii wedge microdisks can be dispersion-tailored to obtain either normal or anomalous group velocity dispersion. In our case, we operate in the normal dispersion regime preventing frequency comb generation by suppressing infrared cascading four-wave mixing. This allows for a clean third harmonic generation at phase-matched visible optical modes. Tunability of the third-harmonic emission is obtained due to a combination of the thermo-optical and Kerr effects. An additional thermal control of the phase matching condition allows for optimizing third-harmonic generation, and agreement between this process and couple-mode theory is demonstrated.