Measurement of the linewidth enhancement factor of injection lasers with a strained active layer

A method for determination of the linewidth enhancement factor α of semiconductor injection lasers is proposed. Experimental values of α, obtained at carrier densities corresponding to pump currents near the threshold value, are reported for InGaAs/GaAs lasers with a strained active layer and for unstrained quantum-well GaAs/GaAIAs lasers. It is shown that in the presence of strain the factor α is 1.9 times less than for conventional quantum-well lasers.