Fig. 2: Experimental generation of soliton crystal (SC) microcombs with different dynamical regions.

a Experimental setup for soliton crystal generation. A continuous-wave (CW) laser drives the crystal generation with the wavelength tuned piezoelectrically. PM: phase modulator, EDFA: erbium-doped fiber amplifier, VNA: vector network analyzer, ESA: electronic spectrum analyzer, and OSA: optical spectrum analyzer. Here the ESA resolution bandwidth is 100 kHz. Inset: Microscope image of device under test. Scale bar: 200 μm. b The generation path of soliton crystals, from nonlinear numerical modeling. We identify six distinct states including primary lines, chaotic states, PSC, chaotic SC, spatial breathers, and stationary SC. c, d Experimental optical spectra of generated microcombs from a 64.8 GHz Si₃N₄ microresonator using forward (blue-to-red) laser sweeping at 27.0 dBm (c) and 25.6 dBm (d) input powers respectively. The white dashed rectangle denotes the region where chaotic soliton crystals stochastically occur. The white dashed circle marks the region where the spacing between adjacent strong spectral lines changes from 46 FSRs to 47 FSRs and subsequently 48 FSRs. e The VNA response plotted against modulation frequency in different SC states. “B” represents the peak induced by spatial breathing. “S” and “C” represents the S- and C-resonances respectively