Fig. 3: Probing the supermode cavity thermal and ultrafast dynamics with an optical vector network analyzer (OVNA).

a The experimental setup of the self-stabilized microcomb characterization. LD laser diode, PM phase modulator, EDFA erbium-doped-fiber-amplifier, PBS polarization beam splitter, VNA vector network analyzer, DAQ data acquisition, PD photodetector, OSA optical spectral analyzer, ESA electrical spectral analyzer. A pump laser in the TM mode is sent to the microresonator and a soliton is generated in the TE mode. We monitor TE and TM power separately using a VNA during the laser sweep until a soliton is formed. Inset i–ii: The microresonator supermodes in the TE and TM polarization showing the clear split mode spectra. Inset iii–iv: The normalized power conversion processes in the weak and strong coupling regimes corresponding to ① and ② at (b, d). b The dynamical cavity supermode evolution with respect to the pump-resonance detuning in the TE polarization measured via the OVNA including ①: the evolved split mode spectra region, ②: the polarization strongly coupled region, ③: the high-noise region, ④: the dual-mode interaction region, ⑤: the solitary wave region. c The representative cavity mode spectra in (b) including the strongly converted TE mode ②, the high-noise mode spectrum including the cavity mode spectrum and the nonlinear broadening mode spectrum induced by stochastic phase response ③, the soliton-induced nonlinear mode spectrum (S-resonance) and the breathing signal ④, ⑤. The S-resonance magnitude depends on the soliton number which overlaps with the cavity mode spectrum (C-resonance). Insets are the expanded views. d The dynamical cavity supermode evolution in the TM polarization showing the power decay region ②, the high-noise region ③, the dual-mode interaction region ④ and ⑤. e The representative cavity mode spectra, and the nonlinear mode spectra induced by the phase response of the intracavity field at the different regions.