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Showing papers on "Light scattering published in 2018"


Journal ArticleDOI
TL;DR: In this paper, the photonic media, when properly randomized to minimize the photon transport mean free path, can be used to coat a black substrate and reduce its temperature by radiative cooling.
Abstract: We demonstrate that photonic media, when properly randomized to minimize the photon transport mean free path, can be used to coat a black substrate and reduce its temperature by radiative cooling Even under strong solar radiation, the substrate temperature could reach substantially below that of the ambient air Our random media that consist of silica microspheres considerably outperform commercially available solar-reflective white paint for daytime cooling We have achieved the outstanding cooling performance through a systematic study on light scattering, which reveals that the structural parameters of the random media for maximum scattering are significantly different from those of the commercial paint We have created the random media to maximize optical scattering in the solar spectrum and to enhance thermal emission in the atmospheric transparency window In contrast to previous studies, our random media do not require expensive processing steps or materials, such as silver, and can be applied to

215 citations


Journal ArticleDOI
TL;DR: The mechanisms of the light scattering by LSPRs, near-field enhancement, and plasmon-induced charge separation based on electron-hole pair excitations can be clarified and reviewed from the viewpoint of these mechanisms rather than material science.
Abstract: Metallic nanoparticles such as silver and gold show localized surface plasmon resonances (LSPRs), which are associated with near-field enhancement effects in the vicinity of nanoparticles. Therefore, strong light–matter interaction is induced by the near-field enhancement effects of LSPRs. Because the resonant wavelength of LSPRs can be easily controlled by the size and shape of the metallic nanoparticles in the visible and near-infrared wavelength range, LSPRs have received considerable attention as optical antennae for light energy conversion systems such as solar cells. LSPRs decay very quickly as a result of light scattering and excitation of electron–hole pairs in the metal itself. However, in addition to the near-field enhancement effect, this light scattering and electron–hole pair excitation, which are known to cause loss of LSPRs, can be utilized as a solar cell enhancement mechanism. Here, we focus on plasmonic solid-state solar cells. The mechanisms of the light scattering by LSPRs, near-field ...

159 citations


Journal ArticleDOI
TL;DR: In this paper, a non-local acousto-optic light scattering was used to produce non-reciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform.
Abstract: Non-reciprocal light propagation is essential to control optical crosstalk and back-scatter in photonic systems. However, realizing high-fidelity non-reciprocity in low-loss integrated photonic circuits remains challenging. Here, we experimentally demonstrate a form of non-local acousto-optic light scattering to produce non-reciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform. In this system, a travelling-wave acoustic phonon driven by optical forces in a silicon waveguide spatiotemporally modulates light in a separate waveguide through linear interband Brillouin scattering. This process extends narrowband optomechanics-based schemes for non-reciprocity to travelling-wave physics, enabling large operation bandwidths of more than 125 GHz and up to 38 dB of non-reciprocal contrast between forward- and backward-propagating optical waves. The modulator operation wavelength is tunable over a 35-nm range by varying the optical drive wavelength. Such travelling-wave acousto-optic interactions provide a promising path toward the realization of broadband, low-loss isolators and circulators within integrated photonics. Non-reciprocal single-sideband modulation and mode conversion are realized in a low-loss integrated silicon waveguide, enabling >125 GHz operation bandwidths and up to 38 dB of non-reciprocal contrast between forward- and backward-propagating waves.

153 citations


Journal ArticleDOI
TL;DR: A perspective detailing the current state-of-the-art technologies for the characterisation of nanoparticles (NPs) in liquid suspension is presented and it is hoped that the manuscript will assist scientists in selecting the appropriate technology for characterising their materials and enabling them to comply with regulatory agencies’ demands for accurate and reliable NP size and concentration data.

146 citations


Journal ArticleDOI
TL;DR: In this paper, the Lorenz-Mie theory is used to describe light scattering by a small spherical particle, a central topic for electromagnetic scattering theory, and some of the basic features of its resonant scattering behavior are covered.
Abstract: Light scattering by a small spherical particle, a central topic for electromagnetic scattering theory, is here considered. In this short review, some of the basic features of its resonant scattering behavior are covered. First, a general physical picture is described by a full electrodynamic perspective, the Lorenz–Mie theory. The resonant spectrum of a dielectric sphere reveals the existence of two distinctive types of polarization enhancement: the plasmonic and the dielectric resonances. The corresponding electrostatic (Rayleigh) picture is analyzed and the polarizability of a homogeneous spherical inclusion is extracted. This description facilitates the identification of the first type of resonance, i.e., the localized surface plasmon (plasmonic) resonance, as a function of the permittivity. Moreover, the electrostatic picture is linked with the plasmon hybridization model through the case of a step-inhomogeneous structure, i.e., a core–shell sphere. The connections between the electrostatic and electrodynamic models are reviewed in the small size limit and details on size-induced aspects, such as the dynamic depolarization and the radiation reaction on a small sphere are exposed through the newly introduced Mie–Pade approximative perspective. The applicability of this approximation is further expanded including the second type of resonances, i.e., the dielectric resonances. For this type of resonances, the Mie–Pade approximation reveals the main character of the two different cases of resonances of either magnetic or electric origin. A unified picture is therefore described encompassing both plasmonic and dielectric resonances, and the resonant conditions of all three different types are extracted as functions of the permittivity and the size of the sphere. Lastly, the directional scattering behavior of the first two dielectric resonances is exposed in a simple manner, namely the Kerker conditions for maximum forward and backscattering between the first magnetic and electric dipole contributions of a dielectric sphere. The presented results address several prominent functional features, aiming at readers with either theoretical or applied interest for the scattering aspects of a resonant sphere.

137 citations


Journal ArticleDOI
TL;DR: Brillouin scattering of photons in the whispering gallery modes by magnons in the magnetostatic modes is experimentally investigated, finding that the conservation of the orbital angular momentum results in different nonreciprocal behavior in the Brillouin light scattering.
Abstract: A ferromagnetic sphere can support optical vortices in the form of whispering gallery modes and magnetic quasivortices in the form of magnetostatic modes with nontrivial spin textures. These vortices can be characterized by their orbital angular momenta. We experimentally investigate Brillouin scattering of photons in the whispering gallery modes by magnons in the magnetostatic modes, zeroing in on the exchange of the orbital angular momenta between the optical vortices and magnetic quasivortices. We find that the conservation of the orbital angular momentum results in different nonreciprocal behavior in the Brillouin light scattering. New avenues for chiral optics and optospintronics can be opened up by taking the orbital angular momenta as a new degree of freedom for cavity optomagnonics.

115 citations


Journal ArticleDOI
TL;DR: In this paper, a traveling-wave acoustic phonon driven via optical forces in a silicon waveguide is used to modulate light in a spatially separate waveguide through a linear inter-band Brillouin scattering process.
Abstract: Achieving nonreciprocal light propagation in photonic circuits is essential to control signal crosstalk and optical back-scatter. However, realizing high-fidelity nonreciprocity in low-loss integrated photonic systems remains challenging. In this paper, we experimentally demonstrate a device concept based on nonlocal acousto-optic light scattering to produce nonreciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform. In this process, a traveling-wave acoustic phonon driven via optical forces in a silicon waveguide is used to modulate light in a spatially separate waveguide through a linear inter-band Brillouin scattering process. We demonstrate up to 38 dB of nonreciprocity with 37 dB of single-sideband suppression. In contrast to prior Brillouin- and optomechanics-based schemes for nonreciprocity, the bandwidth of this scattering process is set through optical phase-matching, not acoustic or optical resonances. As a result, record-large bandwidths in excess of 125 GHz are realized, with potential for significant further improvement through optical dispersion engineering. Tunability of the nonreciprocal modulator operation wavelength over a 35 nm bandwidth is demonstrated by varying the optical pump wavelength. Such traveling-wave acousto-optic modulators provide a promising path toward the realization of broadband, low-loss isolators and circulators in integrated photonic circuits.

111 citations


Journal ArticleDOI
01 Feb 2018-Small
TL;DR: This work demonstrates that the integration of nanoparticle-dispersed capacitor elements into an array readily yields a real-time pressure monitoring application and a fully functional touch device capable of acting as a pressure sensor-based input device, thereby opening up new avenues to establish processing techniques that are effective on the nanoscale yet applicable to macroscopic processing.
Abstract: The fundamental challenge in designing transparent pressure sensors is the ideal combination of high optical transparency and high pressure sensitivity. Satisfying these competing demands is commonly achieved by a compromise between the transparency and usage of a patterned dielectric surface, which increases pressure sensitivity, but decreases transparency. Herein, a design strategy for fabricating high-transparency and high-sensitivity capacitive pressure sensors is proposed, which relies on the multiple states of nanoparticle dispersity resulting in enhanced surface roughness and light transmittance. We utilize two nanoparticle dispersion states on a surface: (i) homogeneous dispersion, where each nanoparticle (≈500 nm) with a size comparable to the visible light wavelength has low light scattering; and (ii) heterogeneous dispersion, where aggregated nanoparticles form a micrometer-sized feature, increasing pressure sensitivity. This approach is experimentally verified using a nanoparticle-dispersed polymer composite, which has high pressure sensitivity (1.0 kPa-1 ), and demonstrates excellent transparency (>95%). We demonstrate that the integration of nanoparticle-dispersed capacitor elements into an array readily yields a real-time pressure monitoring application and a fully functional touch device capable of acting as a pressure sensor-based input device, thereby opening up new avenues to establish processing techniques that are effective on the nanoscale yet applicable to macroscopic processing.

106 citations


Book
04 Oct 2018
TL;DR: The effects of the finite size of the primary spheres have been numerically delineated and the two methods obtained in this tutorial paper directly from the monochromatic Maxwell curl equations have been equivalent.
Abstract: Smoke agglomerates are made of many soot sphcres, and their light scattering response is of interest in fire research. The numerical techniques chiefly used for theoretical scattering studies are the method of moments and the coupled dipole moment. The two methods have been obtained in this tutorial paper directly from the monochromatic Maxwell curl equations and shown to be equivalent. The effects of the finite size of the primary spheres have been numerically delineated.

95 citations


Journal ArticleDOI
TL;DR: Colloidally synthesized Mg offers a route to inexpensive, stable nanoparticles with novel shapes and resonances spanning the entire UV-vis-NIR spectrum, making them a flexible addition to the nanoplasmonics toolbox.
Abstract: Nanoparticles of some metals (Cu/Ag/Au) sustain oscillations of their electron cloud called localized surface plasmon resonances (LSPRs). These resonances can occur at optical frequencies and be driven by light, generating enhanced electric fields and spectacular photon scattering. However, current plasmonic metals are rare, expensive, and have a limited resonant frequency range. Recently, much attention has been focused on earth-abundant Al, but Al nanoparticles cannot resonate in the IR. The earth-abundant Mg nanoparticles reported here surmount this limitation. A colloidal synthesis forms hexagonal nanoplates, reflecting Mg’s simple hexagonal lattice. The NPs form a thin self-limiting oxide layer that renders them stable suspended in 2-propanol solution for months and dry in air for at least two week. They sustain LSPRs observable in the far-field by optical scattering spectroscopy. Electron energy loss spectroscopy experiments and simulations reveal multiple size-dependent resonances with energies acr...

79 citations


Journal ArticleDOI
TL;DR: In this article, a machine-learning approach for light control was developed using pairs of binary intensity patterns and intensity measurements. And the authors demonstrated that NNs can be used to find a functional relationship between transmitted and reflected speckle patterns.
Abstract: Scattering often limits the controlled delivery of light in applications such as biomedical imaging, optogenetics, optical trapping, and fiber-optic communication or imaging. Such scattering can be controlled by appropriately shaping the light wavefront entering the material. Here, we develop a machine-learning approach for light control. Using pairs of binary intensity patterns and intensity measurements we train neural networks (NNs) to provide the wavefront corrections necessary to shape the beam after the scatterer. Additionally, we demonstrate that NNs can be used to find a functional relationship between transmitted and reflected speckle patterns. Establishing the validity of this relationship, we focus and scan in transmission through opaque media using reflected light. Our approach shows the versatility of NNs for light shaping, for efficiently and flexibly correcting for scattering, and in particular the feasibility of transmission control based on reflected light.

Journal ArticleDOI
TL;DR: In this paper, a method to counteract wave diffusion and to focus multiple-scattered waves at the deeply embedded target is presented, and the authors experimentally inject light into the reflection eigenchannels of a specific flight time to preferably enhance the intensity of those multiple scattered waves that have interacted with the target object.
Abstract: The efficient delivery of light energy is a prerequisite for the non-invasive imaging and stimulating of target objects embedded deep within a scattering medium. However, the injected waves experience random diffusion by multiple light scattering, and only a small fraction reaches the target object. Here, we present a method to counteract wave diffusion and to focus multiple-scattered waves at the deeply embedded target. To realize this, we experimentally inject light into the reflection eigenchannels of a specific flight time to preferably enhance the intensity of those multiple-scattered waves that have interacted with the target object. For targets that are too deep to be visible by optical imaging, we demonstrate a more than tenfold enhancement in light energy delivery in comparison with ordinary wave diffusion cases. This work will lay a foundation to enhance the working depth of imaging, sensing and light stimulation.

Journal ArticleDOI
Fei Liu1, Pingli Han1, Yi Wei1, Kui Yang1, Huang Shengzhi1, Xuan Li1, Guang Zhang, Lu Bai1, Xiaopeng Shao1 
TL;DR: An active polarization imaging technique, based on wavelength selection, for seeing through highly turbid water where targets are always visually lost, is proposed and experimentally demonstrated.
Abstract: We hereby proposed and experimentally demonstrated an active polarization imaging technique, based on wavelength selection, for seeing through highly turbid water where targets are always visually lost. The method was realized by making use of the dependence of light scattering on wavelength in turbid water. Red light illumination was selected to minimize scattering occurring in light propagation and to guarantee accurate estimation of degree of polarization. Experiments demonstrate its contribution to turn targets in highly turbid water from “undetectable” to “detectable.”

Journal ArticleDOI
Mengran Wang1, Chunyan Wu1, David Sinefeld1, Bo Li1, Fei Xia1, Chris Xu1 
TL;DR: A systematic study of in vivo three-photon imaging at different excitation wavelengths and quantified the tissue attenuation, providing unequivocal validation of the theoretical estimations based on water absorption and tissue scattering in predicting the effective attenuation lengths for long wavelength in vivo imaging.
Abstract: Light attenuation in thick biological tissues, caused by a combination of absorption and scattering, limits the penetration depth in multiphoton microscopy (MPM). Both tissue scattering and absorption are dependent on wavelengths, which makes it essential to choose the excitation wavelength with minimum attenuation for deep imaging. Although theoretical models have been established to predict the wavelength dependence of light attenuation in brain tissues, the accuracy of these models in experimental settings needs to be verified. Furthermore, the water absorption contribution to the tissue attenuation, especially at 1450 nm where strong water absorption is predicted to be the dominant contributor in light attenuation, has not been confirmed. Here we performed a systematic study of in vivo three-photon imaging at different excitation wavelengths, 1300 nm, 1450 nm, 1500 nm, 1550 nm, and 1700 nm, and quantified the tissue attenuation by calculating the effective attenuation length at each wavelength. The experimental data show that the effective attenuation length at 1450 nm is significantly shorter than that at 1300 nm or 1700 nm. Our results provide unequivocal validation of the theoretical estimations based on water absorption and tissue scattering in predicting the effective attenuation lengths for long wavelength in vivo imaging.

Journal ArticleDOI
TL;DR: In this article, the authors report a new strategy to design ratiometric sensors by combining fluorescence and light scattering, two different and independent signals, based on the principles of fluorescence, light scattering and diffraction.
Abstract: Simultaneous response of fluorescence and light scattering can be obtained by using nanomaterials with size- and shape-dependent physiochemical properties. On the basis of this principle, we report a new strategy to design ratiometric sensors by combining fluorescence and light scattering, two different and independent signals. To obtain fluorescence and scattering signals simultaneously under the same excitation, two signal collection strategies are proposed based on the principles of fluorescence, light scattering and diffraction. One is to collect normal (down-conversion) fluorescence and second-order scattering (SOS) signals, and the other is to record the fluorescence excited by the second-order diffraction light of excitation wavelength λ/2 (SODL-fluorescence) and first-order scattering (FOS) or frequency doubling scattering (FDS) signals. A proof of concept study has been performed by using a carbon dots (CDs) and cobalt oxyhydroxide (CoOOH) nanoflakes system for ascorbic acid (AA) sensing. Apart from construction of ratiometric sensors, the combined fluorescence and scattering can also act as a useful technique to monitor aggregation-induced fluorescence quenching or enhancement.

Journal ArticleDOI
TL;DR: By manipulating a given single point spread function, depth-resolved imaging through a thin scattering medium can be extended beyond the original depth of field (DOF) and it is expected to have important applications in science, technology, bio-medical, security and defense.
Abstract: Human ability to visualize an image is usually hindered by optical scattering. Recent extensive studies have promoted imaging technique through turbid materials to a reality where color image can be restored behind scattering media in real time. The big challenge now is to recover objects in a large field of view with depth resolving ability. Based on the existing research results, we systematically study the physical relationship between speckles generated from objects at different planes. By manipulating a given single point spread function, depth-resolved imaging through a thin scattering medium can be extended beyond the original depth of field (DOF). Experimental testing of standard scattering media shows that the DOF can be extended up to 5 times and the physical mechanism is depicted. This extended DOF is benefit to 3D imaging through scattering environment, and it is expected to have important applications in science, technology, bio-medical, security and defense.

Journal ArticleDOI
20 Aug 2018
TL;DR: In this paper, an autocorrelations between the two normal modes of oscillation determined by the center-of-mass and the relative positions of the two-particle system is investigated.
Abstract: Coupling between mesoscopic particles levitated in vacuum is a prerequisite for the realization of a large-scale array of particles in an underdamped environment as well as potential studies at the classical–quantum interface. Here, we demonstrate for the first time, to the best of our knowledge, optical binding between two rotating microparticles mediated by light scattering in vacuum. We investigate autocorrelations between the two normal modes of oscillation determined by the center-of-mass and the relative positions of the two-particle system. The inter-particle coupling, as a consequence of optical binding, removes the degeneracy of the normal mode frequencies, which is in good agreement with theory. We further demonstrate that the optically bound array of rotating microparticles retains their optical coupling during gyroscopic cooling, and exhibits cooperative motion whose center-of-mass is stabilized.

Journal ArticleDOI
TL;DR: Recent spectacular advances in filamentation of ultra-short TW-class lasers are reviewed both in the laboratory and in the field, their underlying mechanisms are revealed, and the applicability of using these new non-linear photonic catalysts for real scale weather control is discussed.
Abstract: Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1-1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015-1017 cm-3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013-1014 W cm-2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the dependence of h-BN optical spectra on nanosheet dimensions and found that the optical extinction coefficient spectrum varied systematically with the lateral size due to the presence of light scattering.
Abstract: For many 2D materials, optical and Raman spectra are richly structured, and convey information on a range of parameters including nanosheet size and defect content. By contrast, the equivalent spectra for h-BN are relatively simple, with both the absorption and Raman spectra consisting of a single feature each, disclosing relatively little information. Here, the ability to size-select liquid-exfoliated h-BN nanosheets has allowed us to comprehensively study the dependence of h-BN optical spectra on nanosheet dimensions. We find the optical extinction coefficient spectrum to vary systematically with nanosheet lateral size due to the presence of light scattering. Conversely, once light scattering has been decoupled to give the optical absorbance spectra, we find the size dependence to be mostly removed save for a weak, but well defined variation in energy of peak absorbance with nanosheet thickness. This finding is corroborated by theoretical calculations. In addition, while we find the position of the sole...


Journal ArticleDOI
TL;DR: In this article, the magnetostatic modes active for Brillouin light scattering in the optical whispering gallery modes of a yttrium iron garnet sphere were identified by magnetic-field dispersion of ferromagnetic-resonance spectroscopy and coupling strength to the known field distribution of the microwave drive antenna.
Abstract: We identify experimentally the magnetostatic modes active for Brillouin light scattering in the optical whispering gallery modes of a yttrium iron garnet sphere. Each mode is identified by magnetic-field dispersion of ferromagnetic-resonance spectroscopy and coupling strength to the known field distribution of the microwave drive antenna. Our optical measurements confirm recent predictions that higher-order magnetostatic modes can also generate optical scattering, according to the selection rules derived from the axial symmetry. From this we summarize the selection rules for Brillouin light scattering. We give experimental evidence that the optomagnonic coupling to nonuniform magnons can be higher than that of the uniform Kittel mode.

Journal ArticleDOI
TL;DR: Transmissive subtractive color filters are proposed and demonstrated that take advantage of an all-dielectric metasurface based on a lattice of TiO2 nanopillars (NPs), rendering a high transmission efficiency that exceeds 90%.
Abstract: Transmissive subtractive color filters are proposed and demonstrated that take advantage of an all-dielectric metasurface based on a lattice of TiO2 nanopillars (NPs), rendering a high transmission efficiency that exceeds 90%. TiO2 NP elements have been created that exhibit a high aspect ratio. Specifically, a series of lithographic processes are conducted to form a narrow and deep hole in the photoresist, which is accompanied by atomic layer deposition of TiO2. A broad palette of vivid colors encompassing the visible band has been obtained by adjusting the NP diameter for a constant duty ratio of 0.35. For the NP resonator, the electric and magnetic field profiles in conjunction with the scattering cross-sections have been meticulously investigated to theoretically validate that the resonant transmission dips are primarily governed by the simultaneous excitation of an electric dipole and a magnetic dipole via Mie scattering.

Journal ArticleDOI
TL;DR: In this paper, the effect of scattering and absorption of CdSe/ZnS QDs on the optical performance for QCLEDs by comparing with the traditional yttrium aluminum garnet phosphor.
Abstract: Quantum dots (QDs) show a great potential for light-emitting diodes (LEDs) packaging, which still face great challenges compared with the matured phosphor downconversion materials. These are probably caused by the unique scattering and absorption properties of QDs, which are extremely different to the traditional phosphor due to their several nanometers size, while their effect on QDs-converted LEDs (QCLEDs) is barely studied. In this paper, we have experimentally and theoretically investigated the effect of scattering and absorption of CdSe/ZnS QDs on the optical performance for QCLEDs by comparing with the traditional yttrium aluminum garnet phosphor. Results indicate that the strong absorption (reabsorption) of QDs causes low radiant efficacy and stability for QCLEDs; their weak scattering also leads to a low color uniformity. It demonstrates that their unique scattering and absorption properties are key factors leading to low optical performance of QCLEDs compared with the traditional phosphor-converted LEDs. For purpose of gaining the white LED with high efficiency and stability, it is highly suggested to use a low QD concentration to reduce the reabsorption loss and the total internal reflection loss. We believe that this paper can provide a better understanding of improving the optical performance for QCLEDs from the prospective of scattering and absorption. In the future, it is important to use low QD concentration to gain high-performance white LEDs with high downconversion efficiency by optimizing packaging structures.

Journal ArticleDOI
TL;DR: In this article, a palm-sized optical PM2.5 sensor has been developed and its performance evaluated and the mass concentration was calculated from the distribution of light scattering intensity by considerin...
Abstract: A new palm-sized optical PM2.5 sensor has been developed and its performance evaluated. The PM2.5 mass concentration was calculated from the distribution of light scattering intensity by considerin...

Journal ArticleDOI
19 Mar 2018-ACS Nano
TL;DR: On the basis of the high conductivity and high transparency of the Ce:In2O3 NC-based composite films, the films are successfully applied as transparent electrodes within an electrochromic device.
Abstract: Charge carrier mobility in transparent conducting oxide (TCO) films is mainly limited by impurity scattering, grain boundary scattering, and a hopping transport mechanism. We enhanced the mobility in nanocrystal (NC)-based TCO films, exceeding even typical values found in sputtered thin films, by addressing each of these scattering factors. Impurity scattering is diminished by incorporating cerium as a dopant in indium oxide NCs instead of the more typical dopant, tin. Grain boundary scattering is reduced by using large NCs with a size of 21 nm, which nonetheless were sufficiently small to avoid haze due to light scattering. In-filling of the precursor solution followed by annealing results in a NC-based composite film which conducts electrons through metal-like transport at room temperature, readily distinguished by the positive temperature coefficient of resistance. Cerium-doped indium oxide (Ce:In2O3) NC-based composite films achieve a high mobility of 56.0 cm2/V·s, and a low resistivity of 1.25 × 10–3...

Journal ArticleDOI
TL;DR: In this article, the authors studied the effects of the variables of monomers per aggregate, which ranged from one to 502, two monomer size parameters of 0.157 and 0.314, and a wide range of refractive index real and imaginary parts.
Abstract: This paper addresses how well and under what conditions the Rayleigh-Debye-Gans (RDG) approximation describes scattering and absorption of light by fractal aggregates (FA) including soot. The RDGFA theory, which is the prevailing, first order description of this problem, has two assumptions: the monomers, or primary particles, of the aggregate scatter and absorb in the Rayleigh regime, and the aggregate scatters in the diffraction limit weighted by this Rayleigh scattering and absorbs as a system of independent monomer particles. The aggregates studied here are formed via Diffusion Limited Cluster Aggregation (DLCA) and have a fractal dimension D = 1.78 ± 0.04 and prefactor of k0 = 1.35 ± 0.10. The aggregates are a collection of monodisperse spherical monomers with point contacts. Optical calculations were performed with the multiple sphere T-matrix (MSTM) and DDSCAT codes for incident light polarized perpendicular to the scattering plane. The scattering considered is the forward scattering intensity and the angular scattering as parameterized by the scattering wave vector. The total absorption cross section for aggregates is also calculated. This work stresses the systematic study of the effects of the variables of monomers per aggregate, which ranged from one to 502, two monomer size parameters of 0.157 and 0.314, and a wide range of refractive index real and imaginary parts. It also considers soot refractive indices with three representative dispersions. A summary of results for both scattering and absorption includes deviations from RDGFA theory ranging as large as 35% with positive deviations increasing with the real part of the refractive index and negative deviations growing with the imaginary part. These deviation from the RDG limit are shown to be similar to deviations for spheres.

Journal ArticleDOI
15 Sep 2018
TL;DR: In this article, the authors perform a first-principles analysis of independent and dependent scattering by a multi-particle group based on the rigorous volume-integral-equation formulation of electromagnetic scattering.
Abstract: The terms “independent” and “dependent” scattering are ubiquitous in the phenomenological discipline of light scattering by particulate media. Yet there is a wide range of ad hoc definitions of these terms, many of which are vague and conceptually inconsequential. In this paper we perform a first-principles analysis of these terms based on the rigorous volume-integral-equation formulation of electromagnetic scattering. We argue that scattering by a multi-particle group can be called independent if certain optical observables for the entire group can be expressed in appropriate single-particle observables. Otherwise one deals with the dependent scattering regime. The prime (and perhaps the only) examples of independent scattering are scattering scenarios described by the first-order-scattering approximation and the first-principles radiative transfer theory.

Journal ArticleDOI
TL;DR: A hybrid metasurface-based perfect absorber which shows the near-unity absorbance and facilities to work as a refractive index sensor and the proposed metadevice possesses potential applications in solar photovoltaic and photodetectors, as well as in organic and bio-chemical detection.
Abstract: We propose a hybrid metasurface-based perfect absorber which shows the near-unity absorbance and facilities to work as a refractive index sensor. We have used the gold mirror to prevent the transmission and used the amorphous silicon (a-Si) nanodisk arrays on top of the gold mirror which helps to excite the surface plasmon by scattering light through it at the normal incident. We numerically investigated the guiding performance. The proposed absorber is polarization independent and shows a maximum absorption of 99.8% at a 932 nm wavelength in the air medium. Considering the real applications, by varying the environments refractive indices from 1.33 to 1.41, the proposed absorber can maintain absorption at more than 99.7%, with a red shift of the resonant wavelength. Due to impedance matching of the electric and magnetic dipoles, the proposed absorber shows near-unity absorbance over the refractive indices range of 1.33 to 1.41, with a zero-reflectance property at a certain wavelength. This feature could be utilized as a plasmonic sensor in detecting the refractive index of the surrounding medium. The proposed plasmonic sensor shows an average sensitivity of 325 nm/RIU and a maximum sensitivity of 350 nm/RIU over the sensing range of 1.33 to 1.41. The proposed metadevice possesses potential applications in solar photovoltaic and photodetectors, as well as in organic and bio-chemical detection.

Journal ArticleDOI
TL;DR: Non-resonant scattering in suspensions of wide-bandgap nanosheets is investigated, and a general model which allows the scattering spectra to be used as metrics for particle size in nanosheet dispersions is developed.
Abstract: Extinction spectra of nanomaterial suspensions can be dominated by light scattering, hampering quantitative spectral analysis. No simple models exist for the wavelength-dependence of the scattering coefficients in suspensions of arbitrary-sized, high-aspect-ratio nanoparticles. Here, suspensions of BN, talc, GaS, Ni(OH)2, Mg(OH)2 and Cu(OH)2 nanosheets are used to explore non-resonant scattering in wide-bandgap 2D nanomaterials. Using an integrating sphere, scattering coefficient (σ) spectra were measured for a number of size-selected fractions for each nanosheet type. Generally, σ scales as a power-law with wavelength in the non-resonant regime: σ(λ)∝[λ/〈L〉]−m, where 〈L〉 is the mean nanosheet length. For all materials, the scattering exponent, m, forms a master-curve, transitioning from m = 4 to m = 2, as the characteristic nanosheet area increases, indicating a transition from Rayleigh to van der Hulst scattering. In addition, once material density and refractive index are factored out, the proportionality constant relating σ to [λ/〈L〉]−m, also forms a master-curve when plotted versus 〈L〉. Quantitative analysis of the extinction spectra of dispersions of 2D materials is complicated by light scattering. Here, the authors investigate non-resonant scattering in suspensions of wide-bandgap nanosheets, and develop a general model which allows the scattering spectra to be used as metrics for particle size in nanosheet dispersions.

Journal ArticleDOI
TL;DR: In this paper, a selection rule that dictates the exchange of orbital angular momenta between the vortices was shown to be responsible for the experimentally observed non-reciprocal Brillouin light scattering.
Abstract: Magnetostatic modes supported by a ferromagnetic sphere have been known as the Walker modes, each of which possesses an orbital angular momentum as well as a spin angular momentum along a static magnetic field. The Walker modes with non-zero orbital angular momenta exhibit topologically non-trivial spin textures, which we call magnetic quasi-vortices. Photons in optical whispering gallery modes supported by a dielectric sphere possess orbital and spin angular momenta forming optical vortices. Within a ferromagnetic, as well as dielectric, sphere, two forms of vortices interact in the process of Brillouin light scattering. We argue that in the scattering there is a selection rule that dictates the exchange of orbital angular momenta between the vortices. The selection rule is shown to be responsible for the experimentally observed nonreciprocal Brillouin light scattering.