Abstract
Since its invention, optical frequency comb has revolutionized a broad range of subjects from metrology to spectroscopy. The recent development of microresonator-based frequency combs (microcombs) provides a unique pathway to create frequency comb systems on a chip. Indeed, microcomb-based spectroscopy, ranging, optical synthesizer, telecommunications and astronomical calibrations have been reported recently. Critical to many of the integrated comb systems is the broad coverage of comb spectra. Here, microcombs of more than two-octave span (450 nm to 2,008 nm) is demonstrated through χ(2) and χ(3) nonlinearities in a deformed silica microcavity. The deformation lifts the circular symmetry and creates chaotic tunneling channels that enable broadband collection of intracavity emission with a single waveguide. Our demonstration introduces a new degree of freedom, cavity deformation, to the microcomb studies, and our microcomb spectral range is useful for applications in optical clock, astronomical calibration and biological imaging.
Highlights
Since its invention, optical frequency comb has revolutionized a broad range of subjects from metrology to spectroscopy
The recent development of dissipated Kerr soliton microcombs[10,11,12,13,14,15,16,17] has enabled applications ranging from spectroscopy to astronomy calibration[18,19,20,21,22,23,24,25]
The same challenge is imposed on microcavity harmonic generation, but it is often overcome by adding additional coupler[29]
Summary
Optical frequency comb has revolutionized a broad range of subjects from metrology to spectroscopy. 1234567890():,; Microresonator-based frequency comb (microcomb) uses Kerr nonlinearity to create parametric gain and offset cavity loss[1] It has been demonstrated in various material platforms including silica[2], CaF2 It was revealed that the chaotic channels in the deformed cavity can assist broadband momentum transformation[39], opening up new possibilities to resolve the challenge in outputting broadband nonlinear emissions from microcavities. In this Article, we report a microcomb spanning from 450 to 2008 nm in a deformed cavity (Fig. 1a). Once the angular momenta of the comb reach the corresponding critical lines of total internal reflections, the comb can be effectively collected by a nanofiber through nearly wavelength-independent refraction process[39]
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