Linewidth enhancement factor in strained quantum well lasers

Abstract
The linewidth enhancement factor α in an In0.2Ga0.8As/GaAs strained‐layer multiple quantum well (MQW) laser has been determined from the spontaneous emission spectra below threshold. The measured α at the lasing wavelength is found to be 1.0 compared to a value of 5 typically observed for InGaAsP/InP double‐heterostructure lasers. The smaller α shows that single wavelength strained MQW lasers may have smaller chirp width under modulation and also smaller cw linewidth.