Fig. 2: Platicon frequency comb generation in microresonator enabled by symmetric frequency engineering.

a Microscope photograph of one of the fabricated microresonators with inner and outer angular gratings. Inset: electron microscopy image of the coupling section of the microring. b Measured transmission spectrum around the pump wavelength 1542 nm. The arrows indicate two mode splittings (MS₁ and MS₂, red) occurring around the pump mode (orange). c Measured TE₀₀ mode dispersion \({D}_{{{{{\mathrm{int}}}}}}\) of the device. \({D}_{2}/2{{{{{\rm{\pi }}}}}}=-8.3{{{{{\rm{MHz}}}}}}\) is obtained by parabolic fitting. d Existence map showing conversion efficiency of the platicon microcombs. e Simulated intensity profiles in the cavity at different input power and frequency detuning (normalized by resonance linewidth κ) indicated in (d). f Measured output optical spectrum at different input power. The gray dashed lines show the simulated output optical spectrum corresponding to different platicon states in (d, e).