Abstract

One of the most intriguing aspects of Vertical-Cavity Surface-Emitting Lasers (VCSEL's) lies in their polarization behaviour, which differs from that of edge-emitting lasers due to the lack of a dominating polarization selection mechanism in the quasi cylindrically symmetric structure. One explanation for the observed polarization switching is of a thermal nature and attributes the switching to the shift (caused by the current heating) of the material gain spectral profile relative to the cavity resonances for the two frequency-split polarization modes¹. This model seems to be contradicted by recent experiments, which reported polarization switching at constant active layer temperature (by applying low duty-cycle short pulses on a constant bias level). These authors propose an alternative model based on the spin dynamics between magnetic sublevels in the semiconductor active material². Nevertheless, thermal effects are recognized to play an important role in the behavior of VCSEL's.

© 1998 IEEE