Enhanced nonlinear optics in coupled optical microcavities with an unbroken and broken parity-time symmetry

Abstract

We present a perturbation technique to study the linear and nonlinear output characteristics of coherent photon transport in a parity-time ($\mathcal{PT}$)-symmetric double-microcavity system where one passive cavity contains a single quantum emitter. It is found that (i) for the linear transmission of a low-power input probe field, the output spectra of the proposed $\mathcal{PT}$-symmetric system exhibit a single transparent resonance dip and two symmetric, strongly amplifying sidebands, i.e., an inverted dipole-induced transparency; and (ii) for the nonlinear transmission of the input probe field, giant optical third-order nonlinearities with high linear transmission rate and vanishing nonlinear absorption can be achieved efficiently when the system parameters are tuned properly so that a $\mathcal{PT}$-symmetry phase transition occurs. The obtained results can be useful for quantum information processing, quantum nondemolition measurements of photons, and optical signal processing.