Fig. 2.

Broadband frequency comb generation. a, b Numerically simulated group-velocity dispersions (GVD) at telecom wavelengths for LN waveguides with different top widths. Anomalous dispersions (GVD < 0) can be achieved for both transverse-magnetic (TM) (a) and transverse-electric (TE) (b) modes. c, d Generated frequency comb spectra when the input laser is tuned into resonance with either TM (c) or TE (d) modes at a pump power of ~300 mW in the bus waveguide. The generated combs have a line spacing of ~ 250 GHz, and span ~300 nm (c) and ~700 nm (d) for TM and TE modes, respectively