Linearly and circularly polarized ultraviolet GaN microcavity polariton lasers

Abstract

A linearly polarized coherent ultraviolet (UV) or deep UV light source is required for biochemical, medical, and other industrial applications. Current planar GaN-based UV lasers have threshold currents ∼10 kA/cm2 or higher. A polariton laser is an inversionless coherent light source operating in the strong coupling regime of light-matter interaction [1]. Exciton-polariton lasers have been realized with suitable semiconductor microcavities with both optical and electrical pumping [2–3]. Coherent emission is produced by spontaneous radiative recombination from a macroscopic, coherent and degenerate exciton-polariton condensate. The non-linear threshold of a polariton laser is expected to be low because it does not require the inversion of electronic population and quantum degeneracy may be reached at very low polariton densities. We have investigated the output polarization characteristics of bulk GaN microcavity exciton-polariton diode lasers at room temperature for the first time. We have also investigated the output circular polarization of spin-polarized GaN polariton lasers in which spin polarized carriers are injected through a ferromagnetic tunnel contact.