Linewidth and α-factor in AlGaAs/GaAs vertical cavity surface emitting lasers

Measurements of the α-factor, the linewidth-power product, and the differential gain in AlGaAs/GaAs vertical cavity surface emitting lasers are presented. The linewidth power product of 95 MHz mW which results in the α-factor of 3.7 is obtained. The α-factor as a ratio of the refractive index and gain derivatives with respect to the carrier density is also estimated. From the small signal modulation measurements of the resonance frequency, a differential gain of 3.7×1016 cm2 is obtained. The estimate of differential effective index is made difficult by an anomalously strong dependence of the emission wavelength on injection current.