Extended Data Fig. 1: Characterization of the soliton state.
a–c, Example soliton state, obtained with a 350 mW pump at 980 nm. Experimentally obtained optical spectra of a single soliton (blue) with their theoretical fit (red dashed) at the ‘through’ (panel a) and ‘drop’ (panel b) ports. In the fit, we use g = 0.08 and Δ = 0.46, with the other parameters reported in the Methods. The operational EDFA gain bandwidth is indicated by the overlay in yellow. The input power to the microchip is 44 mW and the measured output powers are 4 mW at the ‘through’, and 6.5 mW in the intracavity ‘drop’ ports, respectively. The insets correspond to the autocorrelation trace, clearly showing one peak per microcavity round-trip. c, Three examples of the intracavity spectrum (blue), displaying the lasing modes within each microcavity resonance and corresponding to the highlighted wavelengths. While the modes are all red detuned, we observe in the mode around 1538 nm, where the peak of the Erbium is located, the coexistence of the soliton red detuned mode with a blue-detuned continuous wave mode in panel a. d-f, Same as panels a–c, for a single soliton with a slightly higher pump power of 360 mW at 980 nm. In the fit we use g = 0.1 and Δ = 0.4, with the other parameter reported in the methods. The input power to the microchip is 63 mW and the measured output powers are 5 mW at the ‘through’, and 8.3 mW at the intracavity ‘drop’ ports. The spectral shape is theoretically fitted by the same model. e, Same as panel c, for the spectrum shown in panel d. g, Radio-frequency spectrum measured around the repetition rate frequency via heterodyne modulation. A small portion of the ‘through’ output signal is processed with an electro-optic modulator, leading to additional sidebands around each of the original comb lines. We considered the third harmonic sidebands, and then set the modulation frequency such that the interaction between adjacent comb-lines produced a f0 = 500 MHz beat-note. Electrical spectrum analyser trace of the signal derived from the amplified photodiode after the electroptic modulation, at 50 MHz span, and resolution bandwidth of 30 kHz. h, Same as panel g but with 1 MHz span, and resolution bandwidth of 10 kHz.
