Search results for "Physics::Optics"

Risken–Nummedal–Graham–Haken instability in class-B lasers

1999

We determine analytical expressions for the Risken-Nummedal-Graham-Haken multimode laser instability outside the uniform field limit in the case of very fast polarization decay (class-B laser). A new condition for the observability of that instability, concerning the value of the cavity mirrors reflectivity, is predicted.

m-bonacci metamaterial multilayers: location of the zero-average index bandgap edges

2009

We examine quasiperiodic multilayers arranged in m-bonacci sequences, which combine ordinary positiveindex materials and dispersive metamaterials with negative index in a certain frequency range. When the volume-averaged refractive index of the nonperiodic multilayer equals zero, the structure does not propagate light radiation and exhibits a forbidden band. We identify some analytical expressions to determine the upper and lower limits of the above zero-average refractive-index bandgap. We recognize that these limits are not explicitly dependent on the geometrical parameters of the stack of layers. © 2009 Optical Society of America. Fil: Monsoriu, J.A.. Universidad Politécnica de Valencia;…

Intensity Invariance of Strong-Field Two-Photon Absorption

2010

We demonstrate experimentally and theoretically the intensity-invariant scaling formula of coherent control of two-photon absorption as a function of pulse-shape parameters of ultrafast laser field in the strong-interaction regime.

2014

We present a unified framework for the description of the interaction of fast electrons with complex nanostructures based on the Green dyadic method. We show that the computation of a generalized field propagator yields the electron energy losses and cathodoluminescence of nano-objects of arbitrary morphologies embedded in complex dielectric media. Spectra and maps for both penetrating and non-penetrating electron trajectories are provided. This numerical approach can be extended to describe complex experiments involving fast electrons and optically excited nanostructures.

Spatial Solitons in Nonlinear Photonic Crystal Fibers

2017

This chapter aims to review the most relevant results on solitons in nonlinear solid-core photonic crystal fibers since their introduction about fifteen years ago. These include fundamental solitons and vortices, as well as vector systems of two fundamental, vortex or mixed components. Also other related systems as solitons in double-core photonic crystal fibers will be reviewed. The presentation will describe the mode families as well as their stability properties. The work is intended to be a comprehensive document on the field and provide a fast update to the reader as well as the necessary sources for a further detailed documentation.

Field propagator of a dressed junction: Fluorescence lifetime calculations in a confined geometry

1997

The study of the fluorescence phenomenon by near-field optical techniques requires one to describe precisely the spontaneous emission change occurring when the fluorescing particle is placed in a complex optical environment. For this purpose, the field susceptibility (also called the field propagator) of a planar junction formed by a cavity bounded by two semi-infinite bodies with arbitrary optical constant is derived within the framework of linear-response theory. The field propagator associated with the junction is then modified in a self-consistent manner to account for the presence of any arbitrary object inside the junction. As a first illustration the alteration of the fluorescence li…

Imaging Surface Plasmons

2012

Controlling surface plasmons is at the heart of plasmonics. Advances in this field are to a large extent triggered by our ability to visualize surface plasmons in their different forms. In this chapter, we provide a review of the different techniques capable of imaging and visualizing surface plasmons. We have divided these techniques in three distinct families: proximal probe techniques, far-field microscopies, and electron imaging. We review here their principal characteristics, advantages, and limitations and illustrate the discussion with images taken from the literature.

Selective excitation of bright and dark plasmonic resonances of single gold nanorods.

2015

Plasmonic dark modes are pure near-field resonances since their dipole moments are vanishing in far field. These modes are particularly interesting to enhance nonlinear light-matter interaction at the nanometer scale because radiative losses are mitigated therefore increasing the intrinsic lifetime of the resonances. However, the excitation of dark modes by standard far field approaches is generally inefficient because the symmetry of the electromagnetic near-field distribution has a poor overlap with the excitation field. Here, we demonstrate the selective optical excitation of bright and dark plasmonic modes of single gold nanorods by spatial phase-shaping the excitation beam. Using two-p…

Light Propagation in Clouds: From Digital Holography to Non-Exponential Extinction

2019

Optical propagation is strongly influenced b y t he n umber concentration, size distribution, thermodynamic phase, and spatial distribution of particles in atmospheric clouds. These properties have been investigated in the field using an airborne digital holographic instrument. A laboratory facility has also been developed, in which optical propagation is being investigated in steady-state turbulent-cloud conditions.

Dark Photon Oscillations in Our Inhomogeneous Universe

2020

A dark photon may kinetically mix with the ordinary photon, inducing oscillations with observable imprints on cosmology. Oscillations are resonantly enhanced if the dark photon mass equals the ordinary photon plasma mass, which tracks the free electron number density. Previous studies have assumed a homogeneous Universe; in this Letter, we introduce for the first time an analytic formalism for treating resonant oscillations in the presence of inhomogeneities of the photon plasma mass. We apply our formalism to determine constraints from Cosmic Microwave Background photons oscillating into dark photons, and from heating of the primordial plasma due to dark photon dark matter converting into …