Fig. 3: Optical frequency combs (OFCs) generated by the adiabatic modulation of the parabolic SNAP bottle microresonator (SBM) with Gaussian spatial distribution of the modulations (SDPMs).
From: Optimized frequency comb spectrum of parametrically modulated bottle microresonators
The SDPM (green line) is defined by \(\xi \left(z/L\right)={e}^{-{\left(z/\sigma \cdot L\right)}^{2}}\), where \(\sigma\) is the dimensionless SDPM width and \(L\) is half the length of the SBM (red line). Rows show the OFC generated with different values of \(\sigma\) for two modulation amplitude maxima: \({\delta \nu }_{{{\mbox{par}}}}=0.1\varDelta {\nu }_{0}=2\) GHz and \({\delta \nu }_{{{\mbox{par}}}}=0.04\varDelta {\nu }_{0}=0.75\) GHz. a A limited number of comb resonances are formed at \(\sigma =0.02\) for both values of \({\delta \nu }_{{{\mbox{par}}}}\), when the SDPM is strongly localized near the centre of the SBM. b–e The OFC spectrum becomes wider and flatter with growing \(\sigma\). For \({\delta \nu }_{{{\mbox{par}}}}=0.75\) GHz, the OFC has a smaller bandwidth, though the power level is ~ 10 dB higher than in the case of \({\delta \nu }_{{{\mbox{par}}}}=2\) GHz. f The generated OFC achieves its optimal shape for a close to uniform SDPM, when \(\sigma =10\).
