The dressed atom as binary phase modulator: towards attojoule/edge optical phase-shift keying

TL;DR

This paper demonstrates that a single two-level quantum system coupled to an optical resonator can induce binary phase shifts on a probe beam with extremely low energy, paving the way for ultra-low power optical communication.

Contribution

It introduces a novel method of binary phase modulation using a single quantum emitter, with potential for deterministic control in nanophotonic devices.

Findings

Single TLS can induce binary phase shifts with energy per switch around 0.23 aJ.

Spontaneous emission causes stochastic phase transitions between positive and negative shifts.

Prospects for deterministic modulation in nanophotonic quantum dot devices are discussed.

Abstract

Nanophotonic technologies offer great promise for ultra-low power optical signal processing, but relatively few nonlinear-optical phenomena have yet been explored as bases for robust digital modulation/switching~\cite{Yang07,Fara08,Liu10,Noza10}. Here we show that a single two-level system (TLS) coupled strongly to an optical resonator can impart binary phase modulation on a saturating probe beam. Our experiment relies on spontaneous emission to induce occasional transitions between positive and negative phase shifts---with each such edge corresponding to a dissipated energy of just one photon ($\approx 0.23$ aJ)---but an optical control beam could be used to trigger additional phase switching at signalling rates above this background. Although our ability to demonstrate controlled switching in our atom-based experiment is limited, we discuss prospects for exploiting analogous physics in a nanophotonic device incorporating a quantum dot as the TLS to realize deterministic binary phase modulation with control power in the aJ/edge regime.