Octave-spanning soliton Kerr microcomb with a record number of comb lines at an electronically detectable repetition rate in a single Si3​N4​ racetrack resonator

We demonstrate generation of an octave-spanning soliton frequency comb in a single 15 GHz silicon nitride racetrack resonator pumped by picosecond pulses synchronized to the cavity repetition rate. The soliton state is achieved with 600 mW of average pump power. Euler bends with adiabatically varying curvature suppress higher-order spatial modes, producing a smooth spectrum with dual dispersive waves. Long directional couplers and low-loss fabrication enable strong high-frequency coupling, allowing efficient extraction of higher-order dispersive waves without precise dispersion engineering. The generated comb spans 24.7 THz (12 fs pulse duration) and contains approximately 8,800 lines, including 4,500 within a 3 dB bandwidth—representing, to our knowledge, the largest number of comb lines reported from a single microresonator.