Monodisperse Silica Spheres Ensembles with Tailored Optical Resonances in the Visible

Montesdeoca, Denise; Bayat, Farzaneh; Espinha, André; Blanco, Alberto; Pecharromán, Carlos; López, Cefe

doi:10.1002/ppsc.201600194

Cited by 12 publications

(15 citation statements)

References 43 publications

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“…15) have a signature in the transport mean free path of randomly assembled Mie scatterers. These resonances were already observed, but up to now, all attempts to describe them more than qualitatively failed [10,13,16]. We argue here that a proper description of resonant near-field effects is the key to a quantitative description of them.In this paper, we present a fit parameter free model that is able to predict for the first time the correct positions (r/λ 0 ) of the resonance peaks of the scattering strength (λ 0 / ) and describes their order of magnitude.…”

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confidence: 67%

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Resonant transport and near-field effects in photonic glasses

et al. 2017

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A fundamental quantity in multiple scattering is the transport mean free path the inverse of which describes the scattering strength of a sample. In this paper, we emphasize the importance of an appropriate description of the effective refractive index n eff in multiple light scattering to accurately describe the light transport in dense photonic glasses. Using n eff as calculated by the energy-density coherent-potential approximation we are able to predict the transport mean free path of monodisperse photonic glasses. This model without any fit parameter is in qualitative agreement with numerical simulations and in fair quantitative agreement with spectrally resolved coherent backscattering measurements on new specially synthesized polystyrene photonic glasses. These materials exhibit resonant light scattering perturbed by strong near-field coupling, all captured within the model. Our model might be used to maximize the scattering strength of high index photonic glasses, which are a key in the search for Anderson localization of light in three dimensions. DOI: 10.1103/PhysRevA.96.043871 Transport phenomena are omnipresent in nature, governing many processes in chemistry, biology, physics, and engineering. Systems as diverse as electrons [1] and ultrasound [2] in condensed matter, mechanical waves in the earth [3], cold atoms in an optical trap [4], and light in disordered photonic materials [5] share the same physical principle [6,7]. Optical experiments are especially appealing because of the absence of photon-photon interaction (unlike in electronic systems) and the existence of relatively high index scattering media such as photonic crystals and glasses. Moreover, optical transport experiments have reached an unprecedented accuracy thanks to the great technological development of sources (e.g., lasers), detectors (e.g., CCDs), and time resolution. All these progresses allow the realization of table-top experiments which highlight the richness of transport phenomena.Wave transport in a diluted disordered suspension of scatterers can be described by the sole far-field properties of the single scatterers. On increasing concentration, however, interference effects due to scatterer-scatterer position correlation need to be taken into account [8]. In this description, the scattering cross section is still the single scatterer one, which, in general, is calculated in the far field. In optics, this approach is expected to fail as soon as the photon scattering mean free path s becomes smaller than a few wavelengths of the light. In this case, the distance between two scattering events is so short that (1) each scattered photon does not reach the far-field limit before being rescattered and (2) the (differential) scattering cross section of each and every scatterer is affected by multiply scattered photons returning to it. A first attempt to describe these near-field effects was recently proposed by Rezvani Naraghi et al. [9], but takes into account only the first point. In this paper, we propose a different light ...

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Resonant transport and near-field effects in photonic glasses

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“…Note that the scattering behavior in this regime was previously studied [20] and fully explained recently. [34,43] Besides the photographs, Figure 2a also shows the experimental and calculated spectra R(λ) converted into colors as perceived by the human eye. The color sensation is approximated via the open-source python module colorpy, [44] which allows to convert any spectrum in the visible range (we use the range λ = [360, 830] nm) into a color space such as Commission internationale de l'éclairage (CIE) xyY or Red Green Blue, making the color printable or displayable on a screen.…”

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The Structural Colors of Photonic Glasses

Schertel

Siedentop

Meijer

et al. 2019

Advanced Optical Materials

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The color of materials usually originates from a combination of wavelength‐dependent absorption and scattering. Controlling the color without the use of absorbing dyes is of practical interest, not only because of undesired bleaching properties of dyes but also regarding minimization of environmental and health issues. Color control without dyes can be achieved by tuning the material's scattering properties in controlling size and spatial arrangement of scatterers. Herein, calibrated photonic glasses (PGs), which are isotropic materials made by random aggregation of nonabsorbing, monodisperse colloidal polystyrene spheres, are used to generate a wide spectral range of purely structural, angular‐independent colors. Experimental reflectance spectra for different sized spheres compare well with a recent theoretical model, which establishes the latter as a tool for color mapping in PGs. It allows to determine the range of visible colors accessible in PGs as function of size, packing fraction, and refractive index of scatterers. It also predicts color saturation on top of the white reflectance as function of the sample's optical thickness. Blue, green, and red are obtained even with low index, while saturated green, cyan, yellow, and magenta can be reached in higher index PGs over several orders of magnitude of sample thickness.

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“…PGs macroscopic in size have been rarely reported so far. Only lower index materials such as polystyrene (PS) [7,[11][12][13][14], poly(methyl methacrylate) (PMMA) [7,12], or silica (SiO 2 ) [15][16][17] were studied. Attempts with higher refractive index materials were done with not perfectly monodisperse zinc sulfide spheres (ZnS, n ZnS = 2.4) dispersed in deionized water or isopropanol [18], or with irregularly shaped TiO 2 particles [19].…”

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Tunable high-index photonic glasses

Schertel

Wimmer

Besirske

et al. 2019

Phys. Rev. Materials

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Materials with extreme photonic properties such as maximum diffuse reflectance, high albedo, or tunable band gaps are essential in many current and future photonic devices and coatings. While photonic crystals, periodic anisotropic structures, are well established, their disordered counterparts, photonic glasses (PGs), are less understood despite their most interesting isotropic photonic properties. Here, we introduce a controlled high index model PG system. It is made of monodisperse spherical TiO2 colloids to exploit strongly resonant Mie scattering for optimal turbidity. We report spectrally resolved combined measurements of turbidity and light energy velocity from large monolithic crack-free samples. This material class reveals pronounced resonances enabled by the possibility to tune both the refractive index of the extremely low polydisperse constituents and their radius. All our results are rationalized by a model based on the energy coherent potential approximation, which is free of any fitting parameter. Surprisingly good quantitative agreement is found even at high index and elevated packing fraction. This class of PGs may be the key to optimized tunable photonic materials and also central to understand fundamental questions such as isotropic structural colors, random lasing or strong light localization in 3D.

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Monodisperse Silica Spheres Ensembles with Tailored Optical Resonances in the Visible

Cited by 12 publications

References 43 publications

Resonant transport and near-field effects in photonic glasses

Resonant transport and near-field effects in photonic glasses

The Structural Colors of Photonic Glasses

Tunable high-index photonic glasses

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