Linewidth enhancement factor of vertical-cavity surface-emitting laser diodes

The linewidth enhancement factor /spl alpha/ characterizes the performance of semiconductor lasers, such as spectral linewidth broadening for CW operation and wavelength chirping under high-frequency modulation. We have for the first time determined the /spl alpha/ factor of vertical-cavity surface-emitting lasers from the measured linewidth-power product and more precisely from the frequency to amplitude modulation ratio at high-frequency current modulation. Both methods provide the same /spl alpha/ factor of 3.7. The minimum linewidth was as narrow as 70 MHz and the linewidth-power product was 5.4 MHz/spl middot/mW neglecting the residual linewidth.<>