Kerr Frequency Comb Generation in Microbottle Resonator with Tunable Zero Dispersion Wavelength

In this letter, we report an optical frequency comb (OFC) generated in a whispering-gallery-mode microbottle resonator, and present a convenient and simple method for adjustment of the zero dispersion wavelength (ZDW). The ZDW tunability of the microbottle resonator realized by exciting modes with different axial mode numbers is predicted theoretically and demonstrated experimentally by changing the coupling position of a tapered fiber. Cascaded four-wave mixing (FWM)-based frequency combs are investigated by pumping the resonator in different dispersion regimes. The results show that the OFC based on degenerated FWM could be generated under the anomalous dispersion, while Raman or Raman-assisted OFC are obtained in the normal dispersion regime.