Calculation of differential gain and linewidth enhancement factor in 980-nm InGaAs vertical cavity surface-emitting lasers

The optimization of differential gain and linewidth enhancement factor within VCSEL's is required to achieve improved performance under dynamic conditions. In this paper, the differential gain and linewidth enhancement factor in an InGaAs-GaAs VCSEL have been calculated over a range of carrier densities and at various wavelengths across the gain spectrum. The results show the importance of low threshold gain values in achieving high differential gain/low linewidth enhancement factor. By temperature tuning the lasing wavelength to shorter wavelengths than the gain peak, values of /spl alpha//sub H/ as low as 0.6 can be achieved.>