Improved Quantum Dot Uniformity and Its Impact on Reflection Sensitivity ( Invited paper )

A semiconductor laser’s sensitivity to parasitic reflections is directly tied to its linewidth enhancement factor. Quantum dot lasers have been shown to have significantly lower linewidth enhancement factors than quantum well lasers with values of zero or even negative values having been theorized for sufficiently uniform dot size distributions. Through optimized growth conditions on silicon, we have obtained highly uniform quantum dots with ultralow linewidth enhancement factors of 0.5 for ground state emission at threshold. Between their low linewidth enhancement factor and strongly damped relaxation oscillation, these lasers show an expected ~17 dB increase in the critical feedback level for coherence collapse relative to state-of-the-art commercial quantum wells.