VCSELs with Stable Linear Polarization Emission Induced by Dielectric Columnar Thin Film Mirrors

Abstract

We propose and analyze numerically new approaches to force the laser emission from VCSELs in a well-defined linear polarization independent of the existing phase and amplitude anisotropies by using dielectric columnar thin-film (CTF) layers in the distributed Bragg reflector (DBR). In one approach, we have demonstrated CTF-VCSELs with top DBR consisting of two alternating CTF layers grown in orthogonally oriented planes and with high and low refractive index for one linear polarization while having the same value of the refractive index value for the orthogonal linear polarization. Such CTF-VCSELs have large dichroism of the mirror losses for two orthogonal linear polarizations. We have also shown DBR designs with parallel columnar orientations of the two CTF dielectric materials. In a second approach, we implement only one CTF layer in the dielectric DBR chosen in such a way that only one linearly polarized longitudinal mode is resonant in the CTF-VCSEL while light with the orthogonally oriented linear polarization is out of resonance and thus cannot lase. Simple estimation of the polarization mode suppression ratio for the different exemplary designs of CTF-VCSELs based on TiO2 and TaO2 dielectric CTFs results in values as high as 80 dB, which compares favorably to the existing alternative approaches.