STRONG POLARIZATION SELECTIVITY IN 780-NM VERTICAL-CAVITY SURFACE-EMITTING LASERS GROWN ON MISORIENTED SUBSTRATES

We report that the 780 nm quantum well vertical-cavity surface-emittin g lasers (VCSELs) grown on a 2 degrees off misoriented (001) substrate toward (111)A exhibit a high polarization suppression ratio over a fe w hundred. The main polarization is always along the [-110] direction for all the lasers over the entire operating currents. To understand t he physical origin of this polarization selectivity, the gain/loss dif ference between two competing polarization modes in VCSELs is investig ated by measuring the subthreshold spectral linewidth. The obtained mo dal gain/loss difference is about 3.0 cm(-1), which is sufficiently la rge for polarization stabilization and amounts to 4% of the threshold modal gain. Comparison with the subthreshold measurement and previous theoretical work shows significant discrepancy, which implies the poss ibility of other polarization selection mechanisms inducing such large gain/loss differences in 780 nm quantum wells grown on a misoriented substrate. In addition, it is found that the 780 nm VCSEL made of a bu lk active medium grown on a misoriented substrate also shows a high po larization selectivity as quantum well lasers. (C) 1997 American Insti tute of Physics.