Experimental properties of injection lasers. III. Current dependence of polarization

Abstract

The power distribution function which describes the shape and current dependence of the lateral beam is applied to a phenomenological model of weakly polarized injection lasers. It predicts that the polarization of coherent power should drop rapidly from an infinite value at threshold to near unity at high drive. Careful measurement of polarization of a laser representative of the model, with especial attention to rejection of the spontaneous emission, supports this conclusion. The form of the power distribution function used in the analysis implies that lasers with strong polarization at high drive have large threshold differences of the two polarizations, suggesting that present theories of the source of polarization are inadequate. The difficulty of interpreting the present results in terms of spatial hole burning or inhomogeneities is pointed out.