Polaritonic non-Hermitian system with single hexagonal microcavity

Abstract

Exciton-polaritons are quasi-particles having hybrid nature of excitons and photons, they can be created and condense into a coherent ground state within a strongly coupled microcavity and can be directly interactive. Group III-nitride semiconductor based microcavity is an excellent platform for investigating polaritonics even at room temperature thanks to its high oscillator strength and large exciton binding energy. Recently, non-Hermitian system with parity–time symmetry (PT symmetry) have attracted considerable attention, and the notion of the PT symmetry has been applied to photonic systems with complementary gain and loss profiles. Due to non-interactive nature of photons, two (or more) identical photonic components have been used to mediate indirect coupling via near-fields in the most of non-Hermitian photonic systems. In this talk, we present direct coupling via exciton nature of polaritons within a single hexagonal microcavity on a loss-modulated substrate. We used a high-quality GaN hexagonal microrod and found the whispering gallery polariton condensate at room temperature [1]. The sixfold-symmetry of the hexagonal microrod offers degenerated modes between two quasiwhispering gallery polariton modes having upwards and downwards triangular paths. By combining the coupled polariton pair with a loss-modulated substrate, the phase transition from unbroken to broken phase was realized, showing a polariton-based PT symmetric system with a single microcavity at room temperature [2]. This polaritonic PT-symmetric platform allows us to investigate non-Hermitian physics and to develop versatile practical applications.