Low RF line width frequency-modulated and amplitude-modulated combs

Monolithic semiconductor quantum dot lasers [1] , [2] are millimeter-sized compact high-precision optical frequency comb sources emitting a spectrum of phase coherent equidistant lines in the near-infrared spectral region. While amplitude-modulated (AM) frequency comb lasers generate a train of optical pulses, frequency-modulated (FM) optical frequency comb lasers emit a quasi continuous-wave output, ideal for on-chip spectroscopy and optical communications. The FM comb state corresponds to splay-phase synchronization, where the inter-modal phases are splayed uniformly around the unit circle, spanning across 2 π [3] , [4] .