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

摘要

Nanophotonic technologies offer great promise for ultra-low power opticalsignal processing, but relatively few nonlinear-optical phenomena have yet beenexplored as bases for robust digitalmodulation/switching~\cite{Yang07,Fara08,Liu10,Noza10}. Here we show that asingle two-level system (TLS) coupled strongly to an optical resonator canimpart binary phase modulation on a saturating probe beam. Our experimentrelies on spontaneous emission to induce occasional transitions betweenpositive and negative phase shifts---with each such edge corresponding to adissipated energy of just one photon ($\approx 0.23$ aJ)---but an opticalcontrol beam could be used to trigger additional phase switching at signallingrates above this background. Although our ability to demonstrate controlledswitching in our atom-based experiment is limited, we discuss prospects forexploiting analogous physics in a nanophotonic device incorporating a quantumdot as the TLS to realize deterministic binary phase modulation with controlpower in the aJ/edge regime.