A possible explanation for the polarization characteristics associated with L-I kinks in 1.3 Mu microns InGaAsP buried heterostructure lasers.

The stimulated emission from mnjection lasers is usually laser polarized in the TE mode. For some 1.3 microns InGaAsP buried heterostructure lasers with a kink in the light-current characteristic, the kink represents the onset of a TM polarized emission (Ref. 2). A possible explanation for this behavior is presented in this paper. The mechanism is essentially 'hole burning' along with (i) higher optical gain of the TM emission that TE in the presence of stress and (ii) larger reflectivity of ther higher order TM modes. The model is supported by (i) experimental observations of higher order TM modes than TE (ii) the observation that the TM gain is unsaturated above TE threshold and (iii) the observation that the TM kink occurs at lower currents as the external pressure is increased. The power output at which a kink appears can be decreased by decreasing the active layer width. The model suggests that channeled substrate buried heterostructure lasers are less likely to have kinks.