Semiclassical scattering of an electric dipole source inside a spherical particle

Lock, James A.

doi:10.1364/josaa.18.003085

Cited by 11 publications

(5 citation statements)

References 31 publications

(45 reference statements)

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“…As shown, there is negligible ASE in the limit Im ǫ → 0, yet the localization of fluctuating dipoles to the gain-half of the (increasingly uniform) sphere leads to a small (though observable) amount of directionality, favoring emission toward the loss direction. The tendency of dipoles within a sphere to emit in a preferred direction has been studied in the context of fluorescence 94 in the ray-optical limit R ≫ c/ω, which as shown here is exacerbated in the presence of gain: 95 essentially, dipoles within a sphere tend to emit in the direction opposite the nearest surface, which explains why spheres having/lacking centro-symmetry tend to emit along directions of gain/loss. Moreover, in order to achieve large directivity, there needs to be a significant amount of mode confinement and gain, as illustrated by the negligible ASE and directivity of the Re ǫ = 2 sphere.…”

Section: Resultsmentioning

confidence: 91%

Amplified and directional spontaneous emission from arbitrary composite bodies: A self-consistent treatment of Purcell effect below threshold

et al. 2016

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We study amplified spontaneous emission (ASE) from wavelength-scale composite bodies-complicated arrangements of active and passive media-demonstrating highly directional and tunable radiation patterns, depending strongly on pump conditions, materials, and object shapes. For instance, we show that under large enough gain, PT symmetric dielectric spheres radiate mostly along either active or passive regions, depending on the gain distribution. Our predictions are based on a recently proposed fluctuating volume-current (FVC) formulation of electromagnetic radiation that can handle inhomogeneities in the dielectric and fluctuation statistics of active media, e.g. arising from the presence of non-uniform pump or material properties, which we exploit to demonstrate an approach to modelling ASE in regimes where Purcell effect (PE) has a significant impact on the gain, leading to spatial dispersion and/or changes in power requirements. The nonlinear feedback of PE on the active medium, captured by the Maxwell-Bloch equations but often ignored in linear formulations of ASE, is introduced into our linear framework by a self-consistent renormalization of the (dressed) gain parameters, requiring the solution of a large system of nonlinear equations involving many linear scattering calculations.Noise in structures comprising passive and active materials can lead to important radiative effects, 1 e.g. spontaneous emission (SE), 2 superluminescence, 3 and fluorescence. 4 Although large-etalon gain amplifiers and related devices have been studied for decades, [5][6][7][8] there is increased interest in the design of wavelength-scale composites for tunable sources of scattering and incoherent emission, 9,10 or which serve as perfect absorbers 11 at mid-infrared and visible wavelengths. In this paper, we extend a recently developed fluctuatingvolume current (FVC) formulation of electromagnetic (EM) fluctuations [12][13][14][15] to the problem of modeling spontaneous emission and scattering from composite, wavelength-scale structures, e.g. metal-dielectric spasers, [16][17][18] subject to inhomogeneities in both material and noise properties. We begin by studying amplified spontaneous emission (ASE) from piecewise-constant composite bodies, showing that their emissivity can exhibit a high degree of directionality, depending sensitively on the gain profile and shape of the objects. For instance, we find that under large enough gain, the directivity of parity-time (PT ) symmetric spheres can be designed to lie primarily along active or passive regions, depending on the presence or absence of centrosymmetry, respectively. Such composite micron-scale emitters act as tunable sources of incoherent radiation, forming a special class of infrared/visible antennas exhibiting polarization-and direction-sensitive absorption and emission properties. An important ingredient for the design of directional emission is the ability to tune the gain profile of the objects, which can be far from homogeneous in realistic settings. Here, we consider tw...

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Section: Resultsmentioning

confidence: 91%

Amplified and directional spontaneous emission from arbitrary composite bodies: A self-consistent treatment of Purcell effect below threshold

et al. 2016

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“…3,4 As r͞a approaches 1, the p ϭ 2 standard rainbow and the p ϭ 1 TIRR merge; this is because a point source located near the edge of the droplet will have the TIR region located almost directly behind it on the nearer edge of the droplet. 2 In principle, TIRRs can exist for all values of p, and the standard rainbow can exist for all p Ն 2, but we do not consider them in this paper, because they become faint; experimentally, we did not see any of the p Ͼ 2 rainbows. 3.…”

Section: Theorymentioning

confidence: 92%

“…2 In this paper we look only at what geometrical optics can tell us about this problem. Figure 1 shows a diagram of a droplet of radius a with a point source of light inside it at a distance r from the center.…”

Section: Theorymentioning

confidence: 99%

Experimental observation of total-internal-reflection rainbows

Adler¹,

Lock²,

Mulholland³

et al. 2003

Appl. Opt.

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A new class of rainbows is created when a droplet is illuminated from the inside by a point light source. The position of the rainbow depends on both the index of refraction of the droplet and the position of the light source, and the rainbow vanishes when the point source is too close to the center of the droplet. Here we experimentally measure the position of the transmission and one-internal-reflection totalinternal-reflection rainbows, and the standard ͑primary͒ rainbow, as a function of light-source position.

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“…This study is indented to provide an in-depth analysis of the depolarization in the framework of Debye's series. The Debye series was first proposed by Debye for an infinite circular cylinder [12], and then has been extensively used for spherical particles [13][14][15][16], coated spherical particles [17][18][19][20][21][22][23], coated cylinder [24] and further extended to spheroidal particles based on the separation of the variable method [25][26]. The recent development of Debye's approach for non-spherical particles with the extended boundary condition method (EBCM) [27][28] is a breakthrough that makes it possible to perform accurate analyzes of the scattering mechanism by non-spherical particles.…”

Section: Introductionmentioning

confidence: 99%

Depolarization of nearly spherical particles: The Debye series approach

Gouesbet

2018

Phys. Rev. A

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Backscattering depolarization of non-spherical particles plays a critical role in active LiDAR retrievals of cloud or aerosol parameters, as well as in particle characterization techniques. However, the interpretation of backscattering light from particles is a challenging research subject. This study addresses the depolarization of nearly spherical particles by using the Debye series approach. Specifically, the T-matrix is represented as an infinite sum of terms; the terms in the expansion are correspondingly associated with diffraction and reflection (p = 0), and multiple transmissions (p > 0) from the particle to medium as waves undergo internal reflections. We found that the enhanced depolarization for optically soft particles stems from multiple transmissions. However, this is mostly from the transmission after one internal reflection (p = 2), when the refractive index is larger than 1.3. Moreover, the interference among multiple transmissions was found to play an essential role in suppressing the depolarization ratio as the refractive index approaches unity. These findings have implications in interpreting the backscattering optical properties of atmospheric aerosols and hydrosols in water.

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Semiclassical scattering of an electric dipole source inside a spherical particle

Cited by 11 publications

References 31 publications

Amplified and directional spontaneous emission from arbitrary composite bodies: A self-consistent treatment of Purcell effect below threshold

Amplified and directional spontaneous emission from arbitrary composite bodies: A self-consistent treatment of Purcell effect below threshold

Experimental observation of total-internal-reflection rainbows

Depolarization of nearly spherical particles: The Debye series approach

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