186 research outputs found
Electro-optical sampling of quantum vacuum fluctuations in dispersive dielectrics
Electro-optical sampling has been recently used to perform
spectrally-resolved measurements of electromagnetic vacuum fluctuations. In
order to understand which information on the ground state of an interacting
system can be acquired thanks to this technique, in this paper we will develop
the quantum theory of electro-optical sampling in arbitrary dispersive
dielectrics. Our theory shows that a measure of the time correlations of the
vacuum fluctuations effectively implements an ellipsometry measurement on the
quantum vacuum, allowing to access the frequency-dependent dielectric function.
We discuss consequences of these results on the possibility to use
electro-optical sampling to probe the population of ground-state virtual
photons in the ultrastrong light-matter coupling regime
Theory of Optical Nonlocality in Polar Dielectrics
Sub-wavelength confinement of mid-infrared light can be achieved exploiting
the metal-like optical response of polar dielectric crystals in their
Reststrahlen spectral region, where they support evanescent modes termed
surface phonon polaritons. In the past few years the investigation of phonon
polaritons localised in nanoresonators and layered heterostructures has enjoyed
remarkable success, highlighting them as a promising platform for mid-infrared
nanophotonic applications. Here we prove that the standard local dielectric
description of phonon polaritons in nanometric objects fails due to the
nonlocal nature of the phonon response and we develop the corresponding
nonlocal theory. Application of our general theory to both dielectric
nanospheres and thin films demonstrates that polar dielectrics exhibit a rich
nonlocal phenomenology, qualitatively different from the one of plasmonic
systems, due to the negative dispersion of phononic optical modes.Comment: 13 pages, 6 figure
Theory of four-wave-mixing in phonon polaritons
Third order anharmonic scattering in light-matter systems can drive a wide
variety of practical and physically interesting processes from lasing to
polariton condensation. Motivated by recent experimental results in the
nonlinear optics of localised phonon polaritons, in this Letter we develop a
quantum theory capable of describing four-wave mixing in arbitrarily
inhomogeneous photonic environments. Using it we investigate Kerr
self-interaction and parametric scattering of surface and localised phonon
polaritons, showing both processes to be within experimental reach.Comment: 20 pages, 3 figure
Light-matter decoupling in the deep strong coupling regime: the breakdown of the Purcell Effect
Improvements in both the photonic confinement and the emitter design have led to a steady increase in the strength of the light-matter coupling in cavity quantum electrodynamics experiments. This has allowed us to access interaction-dominated regimes in which the state of the system can only be described in terms of mixed light-matter excitations. Here we show that, when the coupling between light and matter becomes strong enough, this picture breaks down, and light and matter degrees of freedom totally decouple. A striking consequence of such a counterintuitive phenomenon is that the Purcell effect is reversed and the spontaneous emission rate, usually thought to increase with the light-matter coupling strength, plummets instead for large enough couplings
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