Electric and magnetic dipolar response of germanium nanospheres: interference effects, scattering anisotropy, and optical forces

Gómez-Medina, R.; García‐Cámara, Braulio; Suárez-Lacalle, I.; González, Francisco; Moreno, Fernando; Nieto‐Vesperinas, M.; Sáenz, Juan José

doi:10.1117/1.3603941

Cited by 191 publications

(177 citation statements)

References 49 publications

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“…In particular, dielectric subwavelength spheres of moderate permittivity like silicon 24,25 present strong magnetic and electric dipolar resonances in the visible, as well as in telecom and near-infrared frequencies, where silicon absorption is negligible, without spectral overlap between quadrupolar and higher-order modes 25 . Similar effects are expected for other semiconductor materials 25,26 like germanium (e E16 in the infrared) and rutile-TiO 2 with an effective permittivity as low as eE6 in the near-infrared. The observation of the strong magnetic response predicted in silicon nanoparticles has recently been reported 27 .…”

supporting

confidence: 77%

“…Interestingly, the spectral proximity between dipolar electric and magnetic responses allows coherent effects between them. In particular, when the absolute values of electric and magnetic polarizabilities are the same, such nonmagnetic particles present differential scattering cross-sections 26 equivalent to those predicted for hypothetical dipolar magnetodielectric particles 8 .…”

mentioning

confidence: 79%

“…The ratio l/(na) constitutes a scaling factor that keeps the effects in the angular distribution of scattered intensity derived from the aforementioned interference between the induced electric and magnetic dipoles, (this magnetodielectric behaviour was actually proven for dielectric cylinders, rescaled from those being made of ceramic in the microwave region to those of Si in the near-infrared 28 ). Here we use the same argument for spheres: the similar value of l/(na) in the experiments carried out in this paper should be compared with that of a Si sphere in the near-infrared 25,26 .…”

mentioning

confidence: 99%

“…Concerning spheres, for a given refractive index n and working wavelength l, it will be possible to select the 'Huygens' source or reflector mode by choosing the appropriate sphere radius a (ref. 26). An all-dielectric Yagi-Uda antenna based on these ideas was recently proposed 6,30 and experimentally tested in the microwave regime 31 .…”

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confidence: 99%

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Magnetic and electric coherence in forward- and back-scattered electromagnetic waves by a single dielectric subwavelength sphere

et al. 2012

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Magnetodielectric small spheres present unusual electromagnetic scattering features, theoretically predicted a few decades ago. However, achieving such behaviour has remained elusive, due to the non-magnetic character of natural optical materials or the difficulty in obtaining low-loss highly permeable magnetic materials in the gigahertz regime. Here we present unambiguous experimental evidence that a single low-loss dielectric subwavelength sphere of moderate refractive index (n ¼ 4 like some semiconductors at near-infrared) radiates fields identical to those from equal amplitude crossed electric and magnetic dipoles, and indistinguishable from those of ideal magnetodielectric spheres. The measured scattering radiation patterns and degree of linear polarization (3-9 GHz/33-100 mm range) show that, by appropriately tuning the a/l ratio, zero-backward ('Huygens' source) or almost zeroforward ('Huygens' reflector) radiated power can be obtained. These Kerker scattering conditions only depend on a/l. Our results open new technological challenges from nanoand micro-photonics to science and engineering of antennas, metamaterials and electromagnetic devices.

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supporting

confidence: 77%

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confidence: 79%

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confidence: 99%

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confidence: 99%

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Magnetic and electric coherence in forward- and back-scattered electromagnetic waves by a single dielectric subwavelength sphere

et al. 2012

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“…On the other hand, as shown in recent theoretical works, interference of magnetic and electric dipole resonances inside high-refractive index dielectric nanoparticles can strongly affect their scattering pattern making it dependent on wavelength 27,28 . For some wavelengths the particles can act as 'Huygens' sources, scattering the whole energy in the forward direction, while for another wavelength range, light is almost completely scattered backward.…”

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confidence: 97%

Directional visible light scattering by silicon nanoparticles

et al. 2013

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Directional light scattering by spherical silicon nanoparticles in the visible spectral range is experimentally demonstrated for the first time. These unique optical properties arise because of simultaneous excitation and mutual interference of magnetic and electric dipole resonances inside a single nanosphere. Such behaviour is similar to Kerker's-type scattering by hypothetic magneto-dielectric particles predicted theoretically three decades ago. Here we show that directivity of the far-field radiation pattern of single silicon spheres can be strongly dependent on the light wavelength and the nanoparticle size. For nanoparticles with sizes ranging from 100 to 200 nm, forward-to-backward scattering ratio above six can be experimentally obtained, making them similar to 'Huygens' sources. Unique optical properties of silicon nanoparticles make them promising for design of novel low-loss visible-and telecom-range metamaterials and nanoantenna devices.

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Titania‐Based Spherical Mie Resonators Elaborated by High‐Throughput Aerosol Spray: Single Object Investigation

Checcucci

Bottein

Claude

et al. 2018

Adv Funct Materials

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10. 1002/adfm.201801958. tives to replace complex and bulky optical elements. This unique ability is due to strong modifications of the local density of optical states occurring in sub-micrometric objects made of materials featuring high dielectric constant and sufficiently small absorption losses.Most studies over the last years have mainly addressed silicon- [4][5][6][7][8][9][10] and germanium-based [11][12][13][14] Mie resonators, demonstrating that they could outperform their metallic counterpart supporting localized plasmonic resonances. However, the large absorption of group IV semiconductor compounds at short wavelengths induces strong optical losses, limiting their potential applicability as efficient devices especially at blue and near-UV frequencies [15,16] (e.g. at 450 nm: n Si = 4.5, k Si = 0.13; n Ge = 4.0, k Ge = 2.24). Furthermore, with a few exception based on colloids [4,17,18] and solid state dewetting, [13,[19][20][21][22][23] typical nanofabrication methods of Si(Ge)-based Mie resonators rely on top-down technologies that are not easy to scale-up at affordable prices.TiO 2 -based optical devices are an interesting alternative to Si, since Titania has a relatively high refractive index and is fully transparent up to UV frequencies [24,25] (e.g.: at 450 nm: n TiO2 = 2.55, k TiO2 = 1.2 × 10 −5 ; at 370 nm: n TiO2 = 2.83, k TiO2 = 1 × 10 −3 ) rendering it, for instance, a strategic material to manipulate the light emitted by conventional GaN-based blue LEDs (at about 450 nm). TiO 2 can be prepared by high-throughput chemical processes, which is a prerequisite for applications requiring large surface systems. It also has many other advantages over Si and metals that are its high chemical, mechanical, and thermal stability, nontoxicity, and relative natural abundance.To date, several groups have studied the properties of Titania particles as dielectric resonators prepared using conventional top-down microfabrication technologies [26][27][28][29][30] or soft-nanoimprint lithography. [31,32] They all confirmed that electromagnetic resonances could be generated within these metal oxide objects. However, the limited exploitation of this material is mainly due to the difficulty in applying conventional top-down fabrication methods to TiO 2 . Additionally, such approaches do not allow the preparation of spherical resonators, [33] which may be interesting for many applications with effective metamaterials, such as beam steering and back-scattering-free optics, [11,[34][35][36][37][38][39][40][41][42][43][44][45]

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Electric and magnetic dipolar response of germanium nanospheres: interference effects, scattering anisotropy, and optical forces

Cited by 191 publications

References 49 publications

Magnetic and electric coherence in forward- and back-scattered electromagnetic waves by a single dielectric subwavelength sphere

Magnetic and electric coherence in forward- and back-scattered electromagnetic waves by a single dielectric subwavelength sphere

Directional visible light scattering by silicon nanoparticles

Titania‐Based Spherical Mie Resonators Elaborated by High‐Throughput Aerosol Spray: Single Object Investigation

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