Quantum Nonlinear Response of Emitter Lattices

TL;DR

This paper explores the quantum nonlinear optical responses of emitter lattices, revealing phenomena like excitonic Bloch states, broadband emission, and bistability, which are distinct from classical analogs and enable control of quantum nonlinearities.

Contribution

It introduces a theoretical framework for quantum nonlinearities in emitter lattices, highlighting phenomena such as Bloch state excitation, broadband emission, and bistability near the wavelength scale.

Findings

Resonant plane waves can excite excitonic Bloch states outside the light cone.

Strong driving leads to broadband photon emission spanning various frequencies.

Bistability occurs near the driving wavelength, enabling control over quantum nonlinearities.

Abstract

We theoretically investigate the emergence of quantum nonlinearities in the optical response of lattices of two-level quantum emitters coherently driven by a laser. For subwavelength lattice periods, where the system behaves as a quantum metasurface, we find that a resonant incident plane wave can populate excitonic Bloch states with parallel wavevectors different from the incident field, including those lying outside the light cone. Closely related to resonance fluorescence, the far-field emission from the system in the strong-driving regime is dominated by a broadband background of photons spanning a wide range of frequencies and wavevectors. Moreover, we show that, for periods approaching the driving wavelength, the emitter lattice enters in a bistable regime due to the renormalization of the driving rate, in striking contrast with its classical (bosonic) analog. This bistable behavior enables the selective activation and deactivation of the optical quantum nonlinearities of the system.