Abstract

High quality factor (Q) whispering-gallery mode (WGM) microcavities have been investigated for nonlinear optics, because they provide strong light confinement. Although the third-order nonlinear susceptibility χ⁽³⁾ is small, third-order nonlinear effects, such as four-wave mixing (FWM), stimulated Raman scattering (SRS), and third-harmonic generation (THG), are pronounced in a high-Q microcavity. One application is frequency comb generation [1] pumped with a continuous-wave (CW) input. We recently demonstrated that a broad bandwidth SRS comb can be obtained in a silica toroid microcavity, and this will allow us to realize broadband visible light generation via THG [2]. Although a high-Q microcavity provides strong confinement, the THG process is not always straightforward because it requires the conversation of both energy and momentum simultaneously. Although it has been predicted that this conversation can be achieved by a transverse mode interaction, where THG is generated in a higher order mode, only a preliminary observation using a toroid microcavity has been reported [2,3].

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