Progress on exciton polariton photonics

Abstract

<p indent="0mm">Control of light-matter interactions is crucial for the development of cavity quantum electrodynamics. In the 1950s, Huang developed a model to describe photon-phonon interactions in solid-state systems. In this model, when a phonon and a photon exchange energy continuously and coherently, the system can reach a strong coupling regime and a new quasiparticle called “polariton” can be formed. Huang’s theory also describes the dispersion of phonon polaritons. This theory has been applied to semiconductors by Hopfield, wherein an exciton and a photon can couple with each other, reaching new eigenmodes called “exciton-polaritons”. Subsequently, vacuum Rabi splitting has been observed in a microcavity that is strongly coupled to a single atom or a single quantum dot. Microcavities of a higher quality factor display macroscopic quantum phenomena such as polariton condensation, superfluidity, and vortices. By applying nanofabrication techniques on the cavity or controlling the beam profile of a pumping laser, various potentials can be induced in polariton systems that enable the manipulation of macroscopic quantum states. Excitons exhibit much larger binding energies and oscillator strengths in emerging materials such as organic semiconductors, perovskites, and two-dimensional semiconductors, providing a new platform to extend polariton physics to room-temperature devices. Microcavity exciton-polaritons are the leading candidate systems for studying quantum optics and condensed matter physics. This review first introduces microcavity exciton-polaritons, including the formation of exciton-polaritons, energy-momentum dispersion of exciton-polaritons, and polariton systems classified by the gain medium. We then introduce several systems to achieve strong coupling and a microspectroscopic technique to investigate exciton-polaritons. The third section provides an analysis of the macroscopic quantum states of exciton-polaritons and describes how to manipulate the quantum state using nanofabrication and optical pumping techniques. The fourth section summarizes several new materials that have been used to study exciton-polaritons at room temperature. The last section summarizes this review, and provides perspectives in both theories and experiments.