Semiconductor microcavities: towards polariton lasers

Abstract

In this review paper we address one of the most rapidly developing new domains of semiconductor optics: light-matter coupling in semiconductor microcavities. Using the non-local dielectric response theory and transfer matrix technique, we show how two-dimensional confinement of a photonic mode coupled to an exciton resonance results in the appearance of two branches of exciton-polaritons, quasi-particles combining properties of photons and excitons. We obtain the dispersion relations of polaritons in microcavities and derive a condition for strong-weak coupling threshold. We show that being bosons, exciton-polaritons are subject to Bose-condensation which might result in emission of a coherent and monochromatic light in the strong coupling regime. A source of such coherent light is referred to as a polariton laser. We show that polariton lasers have theoretically no threshold and require essentially new basic physics as compared to conventional lasers described by Einstein theory. We give examples of model polariton laser structures expected to work at room temperature and overview the main difficulties on the way to producing these new opto-electronic devices.