Improved frequency comb operation of an InAs/GaAs hybrid multisection quantum dot laser on silicon

This work reports on a systematic investigation of the frequency comb enhancement in hybrid InAs/GaAs multisection quantum dot lasers on silicon. The colliding configuration provides an operating frequency at twice the fundamental frequency of the free-spectral range of the cold cavity. In particular, the contribution of the linewidth enhancement factor, or a(H)-factor, on the comb formation is investigated with respect to the reverse voltage and temperature conditions. When those parameters are varied, the formation of the combs is found to increase with respect to a(H). In addition, we also demonstrate that this quantum dot laser exhibits a comb behavior, while the beatnote locking is not fully achieved. This effect is essentially due to the dispersion which is not fully compensated from the optical nonlinearities. These results bring further insights on comb and pulse formations in multisection quantum dot lasers, which is important for designing future light sources for on-chip and chip-to-chip optical interconnects.