Microscopical model for polarization stability in optically anisotropic VCSELs

A comparative study between microscopic and macroscopic models describing polarization switching in optically anisotropic VCSELs is presented. The microscopic model includes: (i) steady-state, many-body multi-band microscopic theory for the optical response of semiconductor quantum wells; (ii) the polarization properties of vectorial eigenmodes of VCSEL structures including mode-dependent losses and frequencies; (iii) realistic model for optical anisotropies resulting from intentional or unintentional strata in an active quantum-well layer. A macroscopic model is derived from this microscopic model. It provides a rigorous generalization of the phenomenological approaches to the description of polarization properties of VCSELs used commonly in the literature. The optical anisotropy of the VCSEL structure is assumed to result from anisotropic strain of the active quantum well material. The valence band anisotropy and heavy-hole light-hole mixing effects determine the system characteristics like anisotropic gain and refractive index. The results of microscopic and macroscopic models agree very well for input/output characteristics of anisotropic VCSELs. Also, the stability properties of polarization eigenmodes are qualitatively the same, although the ranges of stability are quantitatively different for both approaches. Incorporation of many-body effects into the analysis usually diminishes the agreement between microscopic and macroscopic theories.