Broad bandwidth third-harmonic generation via four-wave mixing and stimulated Raman scattering in a microcavity

Abstract

We generate broad bandwidth visible light ranging from 498 to 611 nm via third-harmonic generation in a silica toroid microcavity. The silica toroid microcavity is fed with a continuous-wave input at a telecom wavelength, where third-harmonic generation follows the generation of an infrared Kerr comb via cascaded four-wave-mixing and stimulated Raman scattering effects. Thanks to these cascaded effects (four-wave mixing, stimulated Raman scattering, and third-harmonic generation) in an ultrahigh-Q microcavity, a broad bandwidth visible light is obtained. The visible light couples with the whispering gallery mode of the cavity by demonstrating the evanescent coupling of the generated visible light with a tapered fiber based on an add-drop configuration.

Transition between Kerr comb and stimulated Raman comb in a silica whispering gallery mode microcavity

“…It should be noted that the wavelength component around 1675 nm is due to the remaining Raman effect, though the power is very weak. Although we often observe the coexistence of the FWM and SRS processes [37,38], particularly when we carefully design the dispersion of the cavity system, here we clearly observed the transition from FWM to the Raman state and then back to the FWM state. The experimental results agree well with the analysis and the simulation, which indicates that the transition from FWM to the Raman-dominant state is present in a silica microcavity system when we try to switch between different-FSR Kerr comb states.…”

“…Hence, this analysis allows us obtain important information about the strategy for choosing the cavity diameter so that we obtain a Raman-dominant state without FWM. The presence of the SRS comb will allow us to obtain broader bandwidth light [37,38]. The result shows that an under coupling condition (Q ext > Q int ) in addition to the choise of a large-FSR (i.e.…”

Ultra-high-Q whispering-gallery mode resonators in the pulsed-pump regime

“…Future work will explore this dynamical regime with further detail. Specific efforts will also be devoted to the understanding of the interplay of these combs with Raman [21][22][23][24][25][26] and Brillouin nonlinearities, [27][28][29][30] as well as possible applications in metrology. 31,32…”

Efficient excitation and phase matching of fiber-coupled degenerate whispering gallery modes

“…The findings shown in Figs. 7 and 8 can be used to a large extend to define criterions for designing the coupling conditions in spherical lasers and nonlinear devices, since they can be used to decide suitable pumping and modal characteristics for optimum performance [36][37][38]. Note that, such formulation and analysis method can be applied to optimize coupling to any type of degenerate WGMs including the transverse magnetic ones.…”