Research

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10 pages, 2434 KiB

Open AccessArticle

Impact of Cubic Symmetry on Optical Activity of Dielectric 8-srs Networks

by Elena Goi, Benjamin P. Cumming and Min Gu

Appl. Sci. 2018, 8(11), 2104; https://doi.org/10.3390/app8112104 - 01 Nov 2018

Cited by 7 | Viewed by 2631

Photonic crystals are engineered structures able to control the propagation and properties of light. Due to this ability, they can be fashioned into optical components for advanced light manipulation and sensing. For these applications, a particularly interesting case study is the gyroid srs-network, [...] Read more.

Photonic crystals are engineered structures able to control the propagation and properties of light. Due to this ability, they can be fashioned into optical components for advanced light manipulation and sensing. For these applications, a particularly interesting case study is the gyroid srs-network, a three-dimensional periodic network with both cubic symmetry and chirality. In this work we present the fabrication and characterization of three-dimensional cubically symmetric 8-srs photonic crystals derived from combination of eight individual gyroid srs-networks. We numerically and experimentally investigate optical properties of these photonic crystals and study in particular, the impact of cubic symmetry on transmission and optical activity (OA). Gyroid photonic crystals fabricated in this work can lead to the development of smaller, cheaper, and more efficient optical components with functionalities that go beyond the concept of lenses. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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18 pages, 877 KiB

Open AccessArticle

Controlling Refraction Using Sub-Wavelength Resonators

by Yue Chen and Robert Lipton

Appl. Sci. 2018, 8(10), 1942; https://doi.org/10.3390/app8101942 - 16 Oct 2018

Cited by 1 | Viewed by 2305

Abstract

We construct metamaterials from sub-wavelength nonmagnetic resonators and consider the refraction of incoming signals traveling from free space into the metamaterial. We show that the direction of the transmitted signal is a function of its center frequency and bandwidth. The directionality of the [...] Read more.

We construct metamaterials from sub-wavelength nonmagnetic resonators and consider the refraction of incoming signals traveling from free space into the metamaterial. We show that the direction of the transmitted signal is a function of its center frequency and bandwidth. The directionality of the transmitted signal and its frequency dependence is shown to be explicitly controlled by sub-wavelength resonances that can be calculated from the geometry of the sub-wavelength scatters. We outline how to construct a medium with both positive and negative index properties across different frequency bands in the near infrared and optical regime. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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10 pages, 3088 KiB

Open AccessArticle

Numerical Study on the Absorption Characteristics of Subwavelength Metallic Gratings Covered with a Lossy Dielectric Layer

by Chi-Young Hwang, Yong-Hae Kim, Ji Hun Choi, Gi Heon Kim, Jong-Heon Yang, Jae-Eun Pi, Hee-Ok Kim and Chi-Sun Hwang

Appl. Sci. 2018, 8(9), 1445; https://doi.org/10.3390/app8091445 - 24 Aug 2018

Viewed by 2906

Abstract

Optical absorbers have been a topic of intense research due to their importance in many applications. In particular, multi-band and perfect absorption features in a desired frequency range are essential in broadband applications. In this work, we numerically studied the absorption properties of [...] Read more.

Optical absorbers have been a topic of intense research due to their importance in many applications. In particular, multi-band and perfect absorption features in a desired frequency range are essential in broadband applications. In this work, we numerically studied the absorption properties of subwavelength metallic gratings coated with a dielectric layer. Here, the structure is considered to be an integration between a resonant cavity and a subwavelength metallic grating. Two appropriately designed structures can exhibit multi-band absorption properties. In addition to the numerical simulation results, we elaborate on determining the appropriate structural parameters that yield the desired spectral absorption profile in the visible range. We also numerically identify critical coupling conditions for perfect absorption. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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15 pages, 2871 KiB

Open AccessFeature PaperArticle

All-Dielectric Metasurfaces with High-Fluorescence-Enhancing Capability

by Masanobu Iwanaga

Appl. Sci. 2018, 8(8), 1328; https://doi.org/10.3390/app8081328 - 09 Aug 2018

Cited by 18 | Viewed by 5198

Abstract

All-dielectric metasurfaces are an emerging subfield in photonics. Light-wave manipulation has been extensively explored in these metasurfaces. Although light–matter interaction has also been investigated in these metasurfaces, only a limited number of studies have been reported to date. Here, we employ Si-rod-array metasurfaces [...] Read more.

All-dielectric metasurfaces are an emerging subfield in photonics. Light-wave manipulation has been extensively explored in these metasurfaces. Although light–matter interaction has also been investigated in these metasurfaces, only a limited number of studies have been reported to date. Here, we employ Si-rod-array metasurfaces to examine their fluorescence-enhancing capability. They were designed to have prominent resonances at the working wavelengths of fluorescent molecules. As a result, we experimentally observed significant fluorescence intensity enhancement, exceeding 1000-fold for a reference substrate that was a non-enhancing, flat Si wafer. Thus, we conclude that the all-dielectric metasurfaces can potentially serve as highly fluorescence-enhancing platforms. Their performance is comparable to the best performance reported for metallic metasurfaces. These results strongly suggest that all-dielectric metasurfaces can contribute to fluorescence-sensing of diverse molecules, including biomolecules. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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13 pages, 2648 KiB

Open AccessFeature PaperArticle

Topological Network Properties of Fractal-Like Metallic Nanoparticle Patterns and Their Effects on Optical Resonances

by Naoya Kihara and Osamu Sakai

Appl. Sci. 2018, 8(8), 1310; https://doi.org/10.3390/app8081310 - 07 Aug 2018

Cited by 2 | Viewed by 2439

Abstract

Fractal-like nanoparticle two-dimensional patterns forming in diffusion-limited aggregation show variant spatial patterns. However, they have invariant statistical properties in their network topologies, even though their formation is completely in self-assembled processes. One of the outputs from these topological properties is optical resonances at [...] Read more.

Fractal-like nanoparticle two-dimensional patterns forming in diffusion-limited aggregation show variant spatial patterns. However, they have invariant statistical properties in their network topologies, even though their formation is completely in self-assembled processes. One of the outputs from these topological properties is optical resonances at invariant frequencies, which is a required feature of a metamaterial alternative. Fractal-like metallic patterns studied here in both experiments and theoretical models exhibit similar resonance frequencies in the infrared-ray range, and they depend on the unit length of nanoparticles composing arbitrary fractal-like structures. The scheme of analysis applied here using complex network theory does not only reveal the topological properties of the nanoparticle network, but points out their optical and possibly other physical potentials arising from their geometrical properties. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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11 pages, 2161 KiB

Open AccessArticle

Mode Profile Shaping in Wire Media: Towards An Experimental Verification

by Taylor Boyd, Jonathan Gratus, Paul Kinsler, Rosa Letizia and Rebecca Seviour

Appl. Sci. 2018, 8(8), 1276; https://doi.org/10.3390/app8081276 - 01 Aug 2018

Cited by 4 | Viewed by 2749

Abstract

We show that an experimentally plausible system consisting of a modulated dielectric wire medium hosted in a metal cavity or waveguide can be used to shape the longitudinal field profile. In addition, a more realistic permittivity is used. These new frequency domain numerical [...] Read more.

We show that an experimentally plausible system consisting of a modulated dielectric wire medium hosted in a metal cavity or waveguide can be used to shape the longitudinal field profile. In addition, a more realistic permittivity is used. These new frequency domain numerical results are a significant step towards justifying the construction of an experimental apparatus to test the field profile shaping in practise. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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8 pages, 2090 KiB

Open AccessArticle

Refractive Index Sensing through Surface Plasmon Resonance in Light-Diffusing Fibers

by Nunzio Cennamo, Luigi Zeni, Ester Catalano, Francesco Arcadio and Aldo Minardo

Appl. Sci. 2018, 8(7), 1172; https://doi.org/10.3390/app8071172 - 18 Jul 2018

Cited by 25 | Viewed by 4080

Abstract

In this paper, we show that light-diffusing fibers (LDF) can be efficiently used as host material for surface plasmon resonance (SPR)-based refractive index sensing. This novel platform does not require a chemical procedure to remove the cladding or enhance the evanescent field, which [...] Read more.

In this paper, we show that light-diffusing fibers (LDF) can be efficiently used as host material for surface plasmon resonance (SPR)-based refractive index sensing. This novel platform does not require a chemical procedure to remove the cladding or enhance the evanescent field, which is expected to give better reproducibility of the sensing interface. The SPR sensor has been realized by first removing the cladding with a simple mechanical stripper, and then covering the unclad fiber surface with a thin gold film. The tests have been carried out using water–glycerin mixtures with refractive indices ranging from 1.332 to 1.394. The experimental results reveal a high sensitivity of the SPR wavelength to the outer medium’s refractive index, with values ranging from ~1500 to ~4000 nm/RIU in the analyzed range. The results suggest that the proposed optical fiber sensor platform could be used in biochemical applications. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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8 pages, 1778 KiB

Open AccessArticle

Active Color Control in a Metasurface by Polarization Rotation

by Minkyung Kim, Inki Kim, Jaehyuck Jang, Dasol Lee, Ki Tae Nam and Junsuk Rho

Appl. Sci. 2018, 8(6), 982; https://doi.org/10.3390/app8060982 - 15 Jun 2018

Cited by 45 | Viewed by 5932

Abstract

Generating colors by employing metallic nanostructures has attracted intensive scientific attention recently, because one can easily realize higher spatial resolution and highly robust colors compared to conventional pigment. However, since the scattering spectra and thereby the resultant colors are determined by the nanostructure [...] Read more.

Generating colors by employing metallic nanostructures has attracted intensive scientific attention recently, because one can easily realize higher spatial resolution and highly robust colors compared to conventional pigment. However, since the scattering spectra and thereby the resultant colors are determined by the nanostructure geometries, only one fixed color can be produced by one design and a whole new sample is required to generate a different color. In this paper, we demonstrate active metasurface, which shows a range of colors dependent on incident polarization by selectively exciting three different plasmonic nanorods. The metasurface, which does not include any tunable materials or external stimuli, will be beneficial in real-life applications especially in the display applications. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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7 pages, 976 KiB

Open AccessArticle

Refractive Index Variation of Magnetron-Sputtered a-Si_1−xGe_x by “One-Sample Concept” Combinatory

by Tivadar Lohner, Benjamin Kalas, Peter Petrik, Zsolt Zolnai, Miklós Serényi and György Sáfrán

Appl. Sci. 2018, 8(5), 826; https://doi.org/10.3390/app8050826 - 21 May 2018

Cited by 6 | Viewed by 3455

Abstract

Gradient a-Si_1−xGe_x layers have been deposited by ”one-sample concept” combinatorial direct current (DC) magnetron sputtering onto one-inch-long Si slabs. Characterizations by electron microscopy, ion beam analysis and ellipsometry show that the layers are amorphous with a uniform thickness, small [...] Read more.

Gradient a-Si_1−xGe_x layers have been deposited by ”one-sample concept” combinatorial direct current (DC) magnetron sputtering onto one-inch-long Si slabs. Characterizations by electron microscopy, ion beam analysis and ellipsometry show that the layers are amorphous with a uniform thickness, small roughness and compositions from

x = 0

to

x = 1

changing linearly with the lateral position. By focused-beam mapping ellipsometry, we show that the optical constants also vary linearly with the lateral position, implying that the optical constants are linear functions of the composition. Both the refractive index and the extinction coefficient can be varied in a broad range for a large spectral region. The precise control and the knowledge of layer properties as a function of composition is of primary importance in many applications from solar cells to sensors. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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12 pages, 4152 KiB

Open AccessArticle

Nanometric Plasmonic Rulers Based on Orthogonal Plasmonic Gap Modes in Metal Nanoblocks

by Tae-Woo Lee, Young Jin Lee, Eunso Shin and Soon-Hong Kwon

Appl. Sci. 2018, 8(3), 386; https://doi.org/10.3390/app8030386 - 06 Mar 2018

Cited by 1 | Viewed by 2423

Abstract

We theoretically propose a three-dimensional (3D) plasmonic ruler based on orthogonal plasmonic gap modes which have different wavelengths. The ruler consists of three silver nanoblocks with two ten-nanometer air gaps. First, in a two-block structure, the lateral displacement of one block can be [...] Read more.

We theoretically propose a three-dimensional (3D) plasmonic ruler based on orthogonal plasmonic gap modes which have different wavelengths. The ruler consists of three silver nanoblocks with two ten-nanometer air gaps. First, in a two-block structure, the lateral displacement of one block can be determined by the absorption spectrum, in which two orthogonal modes are observed with different wavelengths. Secondly, in a three-block structure, due to the distinctive wavelength dependencies on the x- or y-directional movement of the two orthogonal modes and the strong dependencies on the air gap size, the 3D positioning of one nanoblock relative to a reference nanoblock can be measured with a 2.5 nm resolution using the spectral positions of the absorption spectrum. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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Review

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16 pages, 5972 KiB

Open AccessFeature PaperReview

Investigation of Hyperbolic Metamaterials

by Tatjana Gric and Ortwin Hess

Appl. Sci. 2018, 8(8), 1222; https://doi.org/10.3390/app8081222 - 25 Jul 2018

Cited by 22 | Viewed by 5386

Abstract

Composites designed by employing metal/dielectric composites coupled to the components of the incident electromagnetic (EM) fields are named metamaterials (MMs), and they display features not observed in nature. This type of artificial media has attracted great interest, resulting in groundbreaking theory that bridges [...] Read more.

Composites designed by employing metal/dielectric composites coupled to the components of the incident electromagnetic (EM) fields are named metamaterials (MMs), and they display features not observed in nature. This type of artificial media has attracted great interest, resulting in groundbreaking theory that bridges the gap between EM and photonic phenomena. Practical applications of MMs have been delayed due to the high losses related to the use of metallic composites, on top of the challenges in manufacturing nanoscale, three-dimensional structures. Novel materials—for instance, graphene or transparent-conducting oxides (TCOs), employed for the production of multilayered MMs—can significantly suppress undesirable losses. It is worthwhile noting that three-layered nanocomposites enable an increase in the frequency range of the surface wave. This work analyzes recent progress in the physics of multilayered MMs. We deliver an outline of key notions, such as effective medium approximation, and present multilayered MMs based on the three-layered structure. An overview of graphene multilayered MMs reveals their ability to support Ferrell–Berreman (FB) modes. We also describe the tunable properties of the multilayered MMs. Full article

(This article belongs to the Special Issue Photonic Metamaterials)

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