How a near-infrared frequency-modulated semiconductor comb laser turns into an amplitude-modulated comb

The transition from frequency-modulated to amplitude-modulated frequency comb operation is studied experimentally in a multi-section InAs/InGaAs quantum dot frequency comb laser. Temporally and spectrally-resolved intensity and phase as well as time and frequency domain analysis allow to identify frequency-modulated and amplitude-modulated comb operation regimes in dependence on the laser gain current and absorber reverse bias voltage.