Noise-induced broadening of a quantum-dash laser optical frequency comb

Single-section quantum dash semiconductor lasers have attracted much attention as an integrated and simple platform for the generation of THz-wide and flat optical frequency combs in the telecom C-band. In this work, we present an experimental method allowing to increase the spectral width of the laser comb by the injection of a broadband optical noise from an external semiconductor optical amplifier that is spectrally overlapped with the quantum dash laser comb. The noise injection induces an amplification of the side modes of the laser comb, which acquire a fixed phase relationship with the central modes of the comb. We demonstrate a broadening of the laser comb by a factor of two via this technique.