710 research outputs found

### Photon localization revisited

In the light of Newton-Wigner-Wightman theorem of localizability question, we
have proposed before a typical generation mechanism of effective mass for
photons to be localized in the form of polaritons owing to photon-media
interactions. In this paper, the general essence of this example model is
extracted in such a form as Quantum Field Ontology associated with
Eventualization Principle, which enables us to explain the mutual relations
back and forth, between quantum fields and various forms of particles in the
localized form of the former.Comment: arXiv admin note: substantial text overlap with arXiv:1101.578

### Signatures of photon localization

Signatures of photon localization are observed in a constellation of
transport phenomena which reflect the transition from diffusive to localized
waves. The dimensionless conductance, g, and the ratio of the typical spectral
width and spacing of quasimodes, \delta, are key indicators of electronic and
classical wave localization when inelastic processes are absent. However, these
can no longer serve as localization parameters in absorbing samples since the
affect of absorption depends upon the length of the trajectories of partial
waves traversing the sample, which are superposed to create the scattered
field. A robust determination of localization in the presence of absorption is
found, however, in steady-state measurements of the statistics of radiation
transmitted through random samples. This is captured in a single parameter, the
variance of the total transmission normalized to its ensemble average value,
which is equal to the degree of intensity correlation of the transmitted wave,
\kappa. The intertwined effects of localization and absorption can also be
disentangled in the time domain since all waves emerging from the sample at a
fixed time delay from an exciting pulse, t, are suppressed equally by
absorption. As a result, the relative weights of partial waves emerging from
the sample, and hence the statistics of intensity fluctuations and correlation,
and the suppression of propagation by weak localization are not changed by
absorption, and manifest the growing impact of weak localization with t.Comment: RevTex 16 pages, 12 figures; to appear in special issue of J. Phys. A
on quantum chaotic scatterin

### Statistical Signatures of Photon Localization

The realization that electron localization in disordered systems (Anderson
localization) is ultimately a wave phenomenon has led to the suggestion that
photons could be similarly localized by disorder. This conjecture attracted
wide interest because the differences between photons and electrons - in their
interactions, spin statistics, and methods of injection and detection - may
open a new realm of optical and microwave phenomena, and allow a detailed study
of the Anderson localization transition undisturbed by the Coulomb interaction.
To date, claims of three-dimensional photon localization have been based on
observations of the exponential decay of the electromagnetic wave as it
propagates through the disordered medium. But these reports have come under
close scrutiny because of the possibility that the decay observed may be due to
residual absorption, and because absorption itself may suppress localization.
Here we show that the extent of photon localization can be determined by a
different approach - measurement of the relative size of fluctuations of
certain transmission quantities. The variance of relative fluctuations
accurately reflects the extent of localization, even in the presence of
absorption. Using this approach, we demonstrate photon localization in both
weakly and strongly scattering quasi-one-dimensional dielectric samples and in
periodic metallic wire meshes containing metallic scatterers, while ruling it
out in three-dimensional mixtures of aluminum spheres.Comment: 5 pages, including 4 figure

### Photon Localization in Resonant Media

We report measurements of microwave transmission over the first five Mie
resonances of alumina spheres randomly positioned in a waveguide. Though
precipitous drops in transmission and sharp peaks in the photon transit time
are found near all resonances, measurements of transmission fluctuations show
that localization occurs only in a narrow frequency window above the first
resonance. There the drop in the photon density of states is found to be more
pronounced than the fall in the photon transit time, leading to a minimum in
the Thouless number.Comment: To appear in PRL; 5 pages, including 5 figure

### Photon localization barrier can be overcome

In contradistinction to a widespread belief that the spatial localization of
photons is restricted by a power-law falloff of the photon energy density,
I.Bialynicki-Birula [Phys. Rev. Lett. 80, 5247 (1998)] has proved that any
stronger -- up to an almost exponential -- falloff is allowed. We are showing
that for certain specifically designed cylindrical one-photon states the
localization is even better in lateral directions. If the photon state is built
from the so-called focus wave mode, the falloff in the waist cross-section
plane turns out to be quadratically exponential (Gaussian) and such strong
localization persists in the course of propagation.Comment: Short communication -- 4 pages, 2 figure

### Photon localization versus population trapping in a coupled-cavity array

We consider a coupled-cavity array (CCA), where one cavity interacts with a
two-level atom under the rotating-wave approximation. We investigate the
excitation transport dynamics across the array, which arises in the atom's
emission process into the CCA vacuum. Due to the known formation of atom-photon
bound states, partial field localization and atomic population trapping in
general take place. We study the functional dependance on the coupling strength
of these two phenomena and show that the threshold values beyond which they
become significant are different. As the coupling strength grows from zero,
field localization is exhibited first.Comment: 9 pages, 5 figures. Replaced one plot in Fig.

### Quantum squeezing generation versus photon localization in a disordered microcavity

We investigate theoretically the nonlinear dynamics induced by an intense
pump field in a disordered planar microcavity. Through a self-consistent
theory, we show how the generation of quantum optical noise squeezing is
affected by the breaking of the in-plane translational invariance and the
occurrence of photon localization. We find that the generation of single-mode
Kerr squeezing for the ideal planar case can be prevented by disorder as a
result of multimode nonlinear coupling, even when the other modes are in the
vacuum state. However, the excess noise is a non-monotonous function of the
disorder amplitude. In the strong localization limit, we show that the system
becomes protected with respect to this fundamental coupling mechanism and that
the ideal quadrature squeezing generation can be obtained

### Looking through the ground glass

We mitiate, and to an extent, motivate our discussion wave propagation through a rendom medium by asking whether we can view or image an object through a light scattering medium. We answer in the affirmative by arguing that the image-bearing ballistic component of light can be time-resolved with respect to the image-blurring diffusive component that has to traverse relatively much longer distance. This leads us to the question of diffusion of light or its absence (localization) in disordered media. We discuss some essential differences between photon localization vis-a-vis electron localization. One of these that makes photon localization much harder to realize experimentally is that the photon energy multilics the dielectric disorder in the Maxwell equation, as a result of which localization is missed in the limit of both the
long wavelength (Rayleigh scattering) and the short wavelength (geometrical optics). The narrow 'window of localization' requires drastic enhancement of effective scattering which is possible by the coincidence of the Mie-resonant scattering and the Bragg-reflection (umklapp) conditions. Photon localization at microwave frequencies (as also the complete photon band gap) has alresdy been achieved by several workers. Localization at visible wavelengths is awaited. We also discuss some fundamental QED effects of photon localization, such as the suppression of spontaneous emission from an excited atom embedded in a random dielectric. We end possibility of a 'mobility-edge' laser

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