13 research outputs found
Scalar Wave Propagation in Random, Amplifying Media: Influence of Localization Effects on Length and Time Scales and Threshold Behavior
We present a detailed discussion of scalar wave propagation and light
intensity transport in three dimensional random dielectric media with optical
gain. The intrinsic length and time scales of such amplifying systems are
studied and comprehensively discussed as well as the threshold characteristics
of single- and two-particle propagators. Our semi-analytical theory is based on
a self-consistent Cooperon resummation, representing the repeated
self-interference, and incorporates as well optical gain and absorption,
modeled in a semi-analytical way by a finite imaginary part of the dielectric
function. Energy conservation in terms of a generalized Ward identity is taken
into account
Coherent transport and symmetry breaking - Laser dynamics of constrained granular matter
We present diagrammatic transport theory including self-consistent nonlinear
enhancement and dissipation in the multiple scattering regime. Our model of
Vollhardt-W\"olfle transport of photons is fit-parameter-free and raises the
claim that the results hold up to the closest packed volume of randomly
arranged ZnO Mie scatterers. We find that a symmetry breaking caused by
dissipative effects of a lossy underlying substrate leads to qualitatively
different physics of coherence and lasing in granular amplifying media.
According to our results, confined and extended mode and their laser thresholds
can be clearly attributed to unbroken and broken spatial symmetry. The
diameters and emission profiles of random laser modes, as well as their
thresholds and the positional-dependent degree of coherence can be checked
experimentally.Comment: New Journal of Physics (accepted 2014
Dynamic light diffusion, Anderson localization and lasing in disordered inverted opals: 3D ab-initio Maxwell-Bloch computation
We report on 3D time-domain parallel simulations of Anderson localization of
light in inverted disordered opals displaying a complete photonic band-gap. We
investigate dynamic diffusion processes induced by femtosecond laser
excitations, calculate the diffusion constant and the decay-time distribution
versus the strength of the disorder. We report evidence of the transition from
delocalized Bloch oscillations to strongly localized resonances in
self-starting laser processes.Comment: 4 pages, 5 figure
Theory Of Light Diffusion In Disordered Media With Linear Absorption Or Gain
We present a detailed, microscopic transport theory for light in strongly scattering disordered systems whose constituent materials exhibit linear absorption or gain. Starting from Maxwell\u27s equations, we derive general expressions for transport quantities such as energy transport velocity, transport mean free path, diffusion coefficient, and absorption/gain length. The approach is based on a fully vectorial treatment of the generalized kinetic equation and utilizes an exact Ward identity (WI). While for loss- and gainless media the WI reflects local energy conservation, the effects of absorption or coherent gain are implemented exactly by additional terms in the WI. As a result of resonant (Mie) scattering from the individual scatterers, all transport quantities acquire strong, frequency-dependent renormalizations, which are, in addition, characteristically modified by absorption or gain. We illustrate the influence of various experimentally accessible parameters on these quanitities for dilute systems. The transport theory presented here may set the stage for a theory of random lasing in three-dimensional disordered media. © 2005 The American Physical Society