Role of packing density and spatial correlations in strongly scattering 3D systems

Pattelli, Lorenzo; Egel, Amos; Lemmer, Uli; Wiersma, Diederik S.

doi:10.1364/optica.5.001037

Cited by 45 publications

(44 citation statements)

References 72 publications

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“…Interestingly, for high‐refractive index, anisotropic systems outperform ensembles of optimized isotropic particles only for aspect ratios larger than 40 (more details in Section S5, Supporting Information). The predicted optimal values of radius ( r 0 = 100nm) and filling fraction (ff = 0.3) for isotropic systems with n = 2.60 are in agreement with those reported in theoretical and experimental studies regarding scattering optimization for titanium‐dioxide particles . Moreover, Figure S2d in the Supporting Information shows that, after exhibiting a strong growth in function of the aspect ratio, between c = 400 and c = 1400, the integrated reflectance shows a less marked dependence on c , with a maximum value at c = 500.…”

Section: Resultssupporting

confidence: 87%

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Role of Anisotropy and Refractive Index in Scattering and Whiteness Optimization

Jacucci

Bertolotti

Vignolini

2019

Advanced Optical Materials

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structure factor) and their specific characteristics (form factor and refractive index). [1][2][3][4] Therefore, most efforts to control light propagation in random systems have been focused upon the optimization of isotropic spatial correlations in highrefractive index systems. These studies had a remarkable impact in many fundamental [5][6][7][8][9][10][11][12][13][14][15][16] and applied phenomena. [17][18][19][20][21] However, the role of anisotropy in multiple scattering systems has been overlooked. In fact, despite the well-known analytical solution for the single scattering, [4,22] the response of an ensemble of randomly arranged anisotropic particles has not been theoretically investigated. The same is valid for the presence of anisotropic structural correlations. Similarly, recent experimental works focused on the fabrication and optical characterization of anisotropic, disordered materials but without proving the role of anisotropy in scattering optimization. [23][24][25][26][27][28][29][30] Here, we study the effect of structural and single-particle anisotropy on the opacity of a material and identify the criteria to improve scattering over a large parameter space, including filling fraction and refractive index. Our work proves that ensembles of uncorrelated, anisotropic particles outperform their isotropic counterpart both for low-and high-refractive indices. In addition, anisotropic, low-refractive index systems not only require a lower amount of material to maximize scattering than isotropic media, but they also exhibit a whiteness comparable to those of high-refractive index materials.Our results showcase how to exploit natural resources (e.g., biopolymers) to replace commercially available white enhancers, made from inorganic high-refractive materials (e.g., TiO 2 ), which have recently raised safety concerns. [31,32] Moreover, our work unveils why anisotropy is an evolutionary-chosen mechanism to optimize scattering in biological systems. Results and DiscussionTo establish a comparison between different disordered materials, we numerically investigated the optical properties of 2D media (see Sections S1 and S2 in the Supporting Information). Exploiting a 2D numerical approach allows to independently vary the structural and form factors of a system, and therefore to disentangle their role in scattering optimization, while avoiding computational burden. In particular, we systematically The ability to manipulate light-matter interaction to tailor the scattering properties of materials is crucial to many aspects of everyday life, from paints to lighting, and to many fundamental concepts in disordered photonics. Light transport and scattering in a granular disordered medium are dictated by the spatial distribution (structure factor) and the scattering properties (form factor and refractive index) of its building blocks. As yet, however, the importance of anisotropy in such systems has not been considered. Here, a systematic numerical survey that disentangles and quantifies the role of different kinds...

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Section: Resultssupporting

confidence: 87%

“…Therefore, most efforts to control light propagation in random systems have been focused upon the optimization of isotropic spatial correlations in high‐refractive index systems. These studies had a remarkable impact in many fundamental and applied phenomena …”

Section: Introductionmentioning

confidence: 99%

Role of Anisotropy and Refractive Index in Scattering and Whiteness Optimization

Jacucci

Bertolotti

Vignolini

2019

Advanced Optical Materials

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“…It has been pointed out that complicated coupled configurations involving multiple meta-atoms can be efficiently studied by describing the meta-atoms in terms of α-tensor (or T-matrix) and using the multiple-scattering theory (MST) [17]. Electromagnetically coupled discrete scattering objects can be self-consistently treated to describe for collective responses of multiple particles [22][23][24] and periodic particle arrays [25][26][27][28][29][30][31], and this approach significantly reduces the calculation loads for complicated, random [32,33], or multi-scale systems [34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Describing Meta-Atoms Using the Exact Higher-Order Polarizability Tensors

Mun

Jang

et al. 2020

ACS Photonics

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In nanophotonics, multipole approach has become an indispensable theoretical framework for analyzing subwavelength meta-atoms and their radiation properties. Thus far, induced multipole moments have frequently used to illustrate the radiating properties of the meta-atoms, but they are excited at a specific illumination and do not fully represent anisotropic meta-atoms. On the other hand, dynamic polarizability (α) tensors contain complete scattering information of the metaatoms, but have not often been considered due to complicated retrieval procedures. In this study, we suggest that exact higher-order α-tensor can be efficiently obtained from T-matrix using simple basis transformation. These higher-order α-tensors are necessary to describe recently reported coupled plasmonic and high-refractive-index particles, which we demonstrate from their retrieved α-tensors. Finally, we show that description of meta-atoms using α-tensors incorporated with multiple-scattering theory vastly extends the applicability of the multipole approach in nanophotonics, allowing accurate and efficient depiction of complicated, random, multi-scale systems. Usage: Preprint.

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“…Recently, some unexpected optical properties like optical transparency [37], enhanced absorption [38] and isotropic photonic band gaps [39][40][41][42] were discovered in 2D and 3D disordered media with certain structural correlations, e.g., the stealthy hyperuniform media. Therefore, structural correlations offer a great opportunity for tailoring the optical properties of disordered materials, with promising applications like structural coloration [43,44], bright white paints [45] and solar energy harvesting [38,[46][47][48][49], etc.Despite these fascinating advancements, however, it is still not fully understood how structural correlations affect optical properties of disordered media, even for an ideally simple system composed of randomly distributed spherical scatterers [45,[50][51][52][53]. In particular, the interplay between structural correlations and near-field as well as far-field electromagnetic interactions among scatterers is still not very clear [50,51,54], especially near single scatterer internal resonances (like Mie resonances for dielectric nanoparticles) at high packing density [55][56][57][58][59].On the other hand, the last three decades have witnessed the rapid development of laser cooling and trapping of atoms to realize ultracold atomic gases with extremely low temperatures on the order of a few nanokelvin [60], which stimulate a wide range of exciting applications like high-precision atomic clocks, quantum information processing, quantum computing and quantum simulation of condensed matter systems and so on [60].…”

mentioning

confidence: 99%

“…Despite these fascinating advancements, however, it is still not fully understood how structural correlations affect optical properties of disordered media, even for an ideally simple system composed of randomly distributed spherical scatterers [45,[50][51][52][53]. In particular, the interplay between structural correlations and near-field as well as far-field electromagnetic interactions among scatterers is still not very clear [50,51,54], especially near single scatterer internal resonances (like Mie resonances for dielectric nanoparticles) at high packing density [55][56][57][58][59].…”

mentioning

confidence: 99%

Near-resonant light transmission in two-dimensional dense cold atomic media with short-range positional correlations

Wang

Zhao

2020

J. Opt. Soc. Am. B

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Light propagation in disordered media is a fundamental and important problem in optics and photonics. In particular, engineering light-matter interaction in disordered cold atomic ensembles is one of the central topics in modern quantum and atomic optics. The collective response of dense atomic gases under light excitation, which crucially depends on the spatial distribution of atoms and the geometry of the ensemble, has important impacts on quantum technologies like quantum sensors, atomic clocks and quantum information storage.Here we analyze near-resonant light transmission in two-dimensional dense ultracold atomic ensembles with short-range positional correlations. Based on the coupled-dipole simulations under different atom number densities and correlation lengths, we show that the collective effects are strongly influenced by those positional correlations, manifested as significant shifts and broadening or narrowing of transmission resonance lines. The results show that mean-field theories like Lorentz-Lorenz relation are not capable of describing such collective effects. We further investigate the statistical distribution of eigenstates, which are significantly affected by the interplay between dipole-dipole interactions and position correlations. This work can provide profound implications on collective and cooperative effects in cold atomic ensembles as well as the study of mesoscopic physics concerning light transport in strongly scattering disordered media. simplest hard-sphere-type correlation which exists in densely packed hard spheres [32] can usually increase the transport mean free path of light [33,34]. Screened Coulomb potential induced positional correlations in nanoparticle colloidal suspensions were found to induce strongly negative asymmetry factor [35,36]. Recently, some unexpected optical properties like optical transparency [37], enhanced absorption [38] and isotropic photonic band gaps [39][40][41][42] were discovered in 2D and 3D disordered media with certain structural correlations, e.g., the stealthy hyperuniform media. Therefore, structural correlations offer a great opportunity for tailoring the optical properties of disordered materials, with promising applications like structural coloration [43,44], bright white paints [45] and solar energy harvesting [38,[46][47][48][49], etc.Despite these fascinating advancements, however, it is still not fully understood how structural correlations affect optical properties of disordered media, even for an ideally simple system composed of randomly distributed spherical scatterers [45,[50][51][52][53]. In particular, the interplay between structural correlations and near-field as well as far-field electromagnetic interactions among scatterers is still not very clear [50,51,54], especially near single scatterer internal resonances (like Mie resonances for dielectric nanoparticles) at high packing density [55][56][57][58][59].On the other hand, the last three decades have witnessed the rapid development of laser cooling and trapping of atoms to r...

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Role of packing density and spatial correlations in strongly scattering 3D systems

Cited by 45 publications

References 72 publications

Role of Anisotropy and Refractive Index in Scattering and Whiteness Optimization

Role of Anisotropy and Refractive Index in Scattering and Whiteness Optimization

Describing Meta-Atoms Using the Exact Higher-Order Polarizability Tensors

Near-resonant light transmission in two-dimensional dense cold atomic media with short-range positional correlations

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