Resonant Optical Absorption and Photothermal Process in High Refractive Index Germanium Nanoparticles

Ishii, Satoshi; Chen, Kai; Okuyama, Hideo; Nagao, Tadaaki

doi:10.1002/adom.201600902

Cited by 38 publications

(32 citation statements)

References 40 publications

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“…This excellent ability of light scattering direction control derives from the unique permittivity of Ge. In the visible and near‐infrared regions, Ge has higher refractive index and extinction coefficient than Si, making it more efficient in field confinement and light absorption. In high‐index dielectric nanoparticles, the electric resonances derived from the oscillation of polarization charges and the magnetic resonances originated from the circular displacement currents excited inside the particle are both supported.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the excitonic Bohr radius of Ge (24.3 nm) is larger than that of Si (4.9 nm), which results in more prominent quantum confinement effects. In optics, Ge has stronger light absorption in the visible region and can be used as a photothermal material by virtue of its higher refractive index and extinction coefficient than silicon . Moreover, the third‐order nonlinear optical coefficient of Ge is one order of magnitude greater than Si, which makes it more efficient in nonlinear optics .…”

Section: Introductionmentioning

confidence: 99%

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Directional Scattering in a Germanium Nanosphere in the Visible Light Region

Yan

Huang

et al. 2017

Advanced Optical Materials

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Recently, all-dielectric materials (ADMs), especially with a high value of the refractive index, are emerging as a promising alternative to plasmonic nanostructures for nanophotonics applications. [9][10][11] Comparing to metallic plasmonic nanostructures, ADMs are superior in low-loss, ultralow light-into-heat conversion [12] and the excitation of both electric and strong magnetic resonances. [13] As a basic building block, high-index ADMs such as silicon [14][15][16][17] (Si), gallium arsenide [18] (GaAs), aluminum gallium arsenide [19] (AlGaAs), and so on have attracted more and more attentions. Among them, Si is the most widely studied one because of its abundance and mature processing technology. Directional infrared and visible light scattering by individual nanoparticles have been first experimentally demonstrated by Geffrin et al. [20] and Fu et al. [15] for Si and by Person et al. [18] for GaAs. At a certain wavelength, the forward-to-backward scattering ratio reaches above six for an individual Si nanoparticle. [15] However, at the peak of scattering cross-section spectrum, the directionality decreases greatly and becomes inefficient. Further, Yan et al. [21] observed the directional Fano resonance in Si nanoparticle dimers in the experiments. The forward-to-backward scattering ratio can be ≈64 at the scattering peak relying on the directional Fano resonance. Besides, magnetically induced forward scattering at visible wavelengths in silicon nanoparticle oligomers has also been demonstrated. [22] Other linear and nonlinear optical properties of Si nanoparticles have been studied in detail by Kivshar and co-workers. [23][24][25] On the contrary, Ge with one of the highest refractive indices has not gotten enough attention, especially in the visible region. Comparing with Si, Ge has a smaller bandgap (E g, Ge = 0.66 eV, E g, Si = 1.12 eV) and higher hole and electron mobilities (4.2 and 2.6 times of Si, respectively). [26] Thus, it is widely used for high-performance photodetection and transistor. In addition, the excitonic Bohr radius of Ge (24.3 nm) is larger than that of Si (4.9 nm), which results in more prominent quantum confinement effects. In optics, Ge has stronger light absorption in the visible region and can be used as a photothermal material by virtue of its higher refractive index and extinction coefficient than silicon. [27] Moreover, the thirdorder nonlinear optical coefficient of Ge is one order of magnitude greater than Si, which makes it more efficient in nonlinear optics. [28] The electric and magnetic dipolar responses of Previous designs of photonic nanoantennas are based on noble metal plasmonic structures, suffering from large ohmic loss and only possessing dipolar plasmon modes. This has driven the intense search for all-dielectric materials (ADMs) beyond noble metals. Here, for the first time, a strong scattering anisotropy in a Ge nanosphere is demonstrated in the visible and nearinfrared regions. The forward-to-backward scattering ratio for an individual Ge nanosphere (150 nm) ca...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Directional Scattering in a Germanium Nanosphere in the Visible Light Region

Yan

Huang

et al. 2017

Advanced Optical Materials

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“…It is due to the dual optical property of plasmonic‐like resonance and Mie‐type resonance (Figure a) . Its absorption ability has gone beyond that of Ge nanoparticles, BiInSe foam, and Al nanoparticles . Te can combine the features of both LSPR‐based absorption and all‐dielectric absorption, to enhance the absorption.…”

Section: Photothermal Evaporationmentioning

confidence: 99%

“…[163] Its absorption ability has gone beyond that of Ge nanoparticles, [214] BiInSe foam, [164] and Al nanoparticles. [215] Te can combine the features of both LSPR-based absorption [45,47,215,216] and all-dielectric absorption, [214,217] to enhance the absorption. As noted in the scattering spectra (Figure 5b), the plasmonic-like resonance contributes to the main scattering of the Te nanoparticles with size smaller than 120 nm.…”

Section: Tellurenementioning

confidence: 99%

Solar‐Inspired Water Purification Based on Emerging 2D Materials: Status and Challenges

et al. 2020

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Water shortage and the energy crisis are two major global challenges in this century. The solution for water crisis should be based on a sustainable energy source. Solar‐inspired water purification is an efficient and green technology for tackling the water challenge using abundant and clean solar energy through photothermal evaporation‐induced water production, photoinduced antimicrobial treatment, and photocatalytic degradation of organic contaminants. 2D nanomaterials draw significant attention for their use these three water‐purification methods because of their large surface area, broadband and strong absorption in the solar spectral range, and efficient photothermal and photocatalytic transformation. Herein, the recent development of 2D nanomaterials applied in photothermal evaporation, photoinduced antimicrobial treatment, and photocatalytic capability is comprehensively overviewed. Various strategies in enhancing the light‐absorption and light‐conversion efficiency for different 2D nanomaterials are presented. The challenges and perspectives of these 2D nanomaterials are further discussed for practical water purification. This Review highlights these green energy–driven water‐purification methods based on emerging 2D materials.

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“…For example, the destructive interference between the electric and magnetic moment in a germanium nanosphere leads to scattering anisotropy . In addition, the absorption of germanium nanospheres appears to be enhanced at Mie resonances . Finally, enhanced third harmonic generation in a single germanium nanodisk has been demonstrated experimentally .…”

Section: Introductionmentioning

confidence: 99%

An All‐Dielectric Metasurface Building Block for the Kerker Effect between Excitons and Nanocavities: Germanium Nanogroove

Huang

Yan

et al. 2017

Advanced Optical Materials

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use noble metallic nanomaterials. [9,10] In recent decades, many groups have brought together plasmonic nanostructures and molecular excitons to form plexcitonic coupling systems. [11] Strong coupling has been observed in many systems, such as silver platelet-J-aggregate nanocomposites, [12] gold nanostar-J-aggregate hybrid systems, [13] and gold nanoshell-J-aggregate complexes. [3] However, plasmonic nanostructures are usually associated with a high level of Joule heating losses at optical frequencies, which limit the efficiency of these coupling systems. [14][15][16] It is also believed that molecular excitons will become instable if the temperature of coupling systems rises, [17] which means that these plexcitonic coupling systems cannot work effectively for a long time. Hence, it is necessary to search for a new type of material to replace the plasmonic nanostructures in these systems.After the demonstration of magnetic dipole resonances of silicon nanospheres in the visible region, [18] all-dielectric materials that could manipulate light at subwavelength scales (similar to metallic materials) were widely studied, especially the high-refractiveindex materials (e.g., silicon, germanium, gallium phosphide, and gallium arsenide). [19][20][21] Simple metallic nanostructures, such as nanospheres or nanorods, can exhibit the electric response only. However, the magnetic response can appear in specially designed metallic nanostructures such as split-ring resonators, U-shape structures, and pairs of nanorods. [22][23][24] Unlike noble metallic materials, all-dielectric materials, even a nanosphere, can support both the electric mode and magnetic mode naturally, which is attributed to the nearly negligible imaginary part of their refractive indices. [19,21,25,26] Because of the magnetic response, a silicon nanoparticle can scatter light asymmetrically as a "Huygens" source. [27] Moreover, directional Fano resonance [28] and magnetic hotspots [29] have been achieved in silicon nanodimers. Therefore, all-dielectric materials may offer an alternative route toward addressing the problems facing plexcitonic coupling systems. Yan et al. generated scattering dark states through the Fano interference between excitons and silicon nanogrooves, [30] and Wang et al. explored resonance coupling in silicon nanosphere-J-aggregate heterostructures and observed a mode Coupling between light and matter has many infusive physical effects and potential applications. Large Rabi splitting energy is achieved in many plasmonic nanostructures; however, these noble metallic materials generally suffer from a high level of Joule heating losses at optical frequencies.As an alternative strategy, all-dielectric materials for manipulating light at the subwavelength scale have attracted enormous interest. However, the understanding of the interactions between all-dielectric nanostructures and molecular excitons remains limited to date. Here, the use of a germanium nanogroove as a new all-dielectric metasurface building block is demonstrated for the ...

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Resonant Optical Absorption and Photothermal Process in High Refractive Index Germanium Nanoparticles

Cited by 38 publications

References 40 publications

Directional Scattering in a Germanium Nanosphere in the Visible Light Region

Directional Scattering in a Germanium Nanosphere in the Visible Light Region

Solar‐Inspired Water Purification Based on Emerging 2D Materials: Status and Challenges

An All‐Dielectric Metasurface Building Block for the Kerker Effect between Excitons and Nanocavities: Germanium Nanogroove

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