Continuous Tuning of Gain Peak Linewidth Enhancement Factor from Negative to Positive with p Doping in InAs QD Laser on Si

We investigate the linewidth enhancement factor of 1.3 μm quantum dot lasers epitaxially grown on silicon. Both the calculation and experiment show small (<;1) linewidth enhancement factor at gain peak due to high dot uniformity. By varying the modulation p doping level, the linewidth enhancement factor at threshold can be continuously changed across zero from negative to positive.