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Special Issue "Metamaterials for Sensing"

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A special issue of Sensors (ISSN 1424-8220).

Deadline for manuscript submissions: closed (31 May 2011)

Special Issue Editor

Guest Editor
Dr. Andrea Alù (Website)

Department of Electrical and Computer Engineering, University of Texas, Austin, TX, USA
Interests: metamaterials; applied and theoretical electromagnetics; optics; nanoparticles and nanomaterials; scattering; antennas; circuits; cloaking; photonic crystals; acoustics

Special Issue Information

Dear Colleagues,

The field of metamaterials and artificial materials has rapidly grown in the last decade, spanning microwave, THz and optical frequencies, with a wide range of applications. One of the most intriguing possibility offered by metamaterials is the large flexibility in their dispersion engineering properties, which may provide novel tools to significantly enhance the sensitivity of practical devices. In this context, concepts like electromagnetically induced transparency, extremely slow waves, large field enhancements, and ultracompact resonances have been successfully established in a variety of metamaterial geometries and setups, providing resonance Q factors and robustness to absorption and disorder superior to those in natural materials. These anomalous features may pave the way to a large set of exciting possibilities to dramatically improve current sensing devices, with applications in biology, medicine, chemistry and other related fields. This special issue of Sensors is specifically devoted to the application of novel metamaterial concepts and geometries for sensing devices with improved sensitivity and resolution.

Dr. Andrea Alù
Guest Editor

Published Papers (6 papers)

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Research

Open AccessArticle Impact of the Excitation Source and Plasmonic Material on Cylindrical Active Coated Nano-Particles
Sensors 2011, 11(9), 9109-9120; doi:10.3390/s110909109
Received: 23 July 2011 / Revised: 23 August 2011 / Accepted: 20 September 2011 / Published: 21 September 2011
Cited by 8 | PDF Full-text (1202 KB) | HTML Full-text | XML Full-text
Abstract
Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field [...] Read more.
Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper) are employed and compared for the nano-shell layers. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessArticle Broadband Wide Angle Lens Implemented with Dielectric Metamaterials
Sensors 2011, 11(8), 7982-7991; doi:10.3390/s110807982
Received: 8 July 2011 / Revised: 11 August 2011 / Accepted: 11 August 2011 / Published: 12 August 2011
Cited by 8 | PDF Full-text (2487 KB) | HTML Full-text | XML Full-text
Abstract
The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter [...] Read more.
The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter arrays. Using the recently developed technique of transformation optics, it is possible to transform the curved focal surface to a flat plane while maintaining the perfect focusing behavior of the Luneburg over a wide field of view. Here we apply these techniques to a lesser-known refractive Luneburg lens and implement the design with a metamaterial composed of a semi-crystalline distribution of holes drilled in a dielectric. In addition, we investigate the aberrations introduced by various approximations made in the implementation of the lens. The resulting design approach has improved mechanical strength with small aberrations and is ideally suited to implementation at infrared and visible wavelengths. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessArticle Novel Sensors Based on the Symmetry Properties of Split Ring Resonators (SRRs)
Sensors 2011, 11(8), 7545-7553; doi:10.3390/s110807545
Received: 1 June 2011 / Revised: 21 July 2011 / Accepted: 22 July 2011 / Published: 29 July 2011
Cited by 42 | PDF Full-text (733 KB) | HTML Full-text | XML Full-text
Abstract
The symmetry properties of split ring resonators (SRRs) are exploited for the implementation of novel sensing devices. The proposed structure consists of a coplanar waveguide (CPW) loaded with movable SRRs on the back substrate side. It is shown that if the SRRs [...] Read more.
The symmetry properties of split ring resonators (SRRs) are exploited for the implementation of novel sensing devices. The proposed structure consists of a coplanar waveguide (CPW) loaded with movable SRRs on the back substrate side. It is shown that if the SRRs are placed with the slits aligned with the symmetry plane of the CPW, the structure is transparent to signal propagation. However, if the symmetry is broken, a net axial magnetic field can be induced in the inner region of the SRRs, and signal propagation is inhibited at resonance. The proposed structures can be useful as alignment sensors, position sensors and angle sensors. This novel sensing principle is validated through experiment. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessArticle Numerical Modeling of Plasmonic Nanoantennas with Realistic 3D Roughness and Distortion
Sensors 2011, 11(7), 7178-7187; doi:10.3390/s110707178
Received: 15 May 2011 / Revised: 4 July 2011 / Accepted: 5 July 2011 / Published: 13 July 2011
Cited by 8 | PDF Full-text (2718 KB) | HTML Full-text | XML Full-text
Abstract
Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically results in a modified enhancement [...] Read more.
Nanostructured plasmonic metamaterials, including optical nanoantenna arrays, are important for advanced optical sensing and imaging applications including surface-enhanced fluorescence, chemiluminescence, and Raman scattering. Although designs typically use ideally smooth geometries, realistic nanoantennas have nonzero roughness, which typically results in a modified enhancement factor that should be involved in their design. Herein we aim to treat roughness by introducing a realistic roughened geometry into the finite element (FE) model. Even if the roughness does not result in significant loss, it does result in a spectral shift and inhomogeneous broadening of the resonance, which could be critical when fitting the FE simulations of plasmonic nanoantennas to experiments. Moreover, the proposed approach could be applied to any model, whether mechanical, acoustic, electromagnetic, thermal, etc, in order to simulate a given roughness-generated physical phenomenon. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessArticle Simulation and Analysis of a Metamaterial Sensor Based on a Microring Resonator
Sensors 2011, 11(6), 5886-5899; doi:10.3390/s110605886
Received: 30 March 2011 / Revised: 15 May 2011 / Accepted: 18 May 2011 / Published: 31 May 2011
Cited by 13 | PDF Full-text (2564 KB) | HTML Full-text | XML Full-text
Abstract
Metamaterials are artificial media structured on a size scale smaller than the wavelength of external stimuli, that may provide novel tools to significantly enhance the sensitivity and resolution of the sensors. In this paper, we derive the dispersion relation of hollow cylindrical [...] Read more.
Metamaterials are artificial media structured on a size scale smaller than the wavelength of external stimuli, that may provide novel tools to significantly enhance the sensitivity and resolution of the sensors. In this paper, we derive the dispersion relation of hollow cylindrical dielectric waveguide, and compute the resonant frequencies and Q factors of the corresponding Whispering-Gallery-Modes (WGM). A metamaterial sensor based on microring resonator operating in WGM is proposed, and the resonance intensity spectrum curves in the frequency range from 185 to 212 THz were studied under different sensing conditions. Full-wave simulations, considering the frequency shift sensitivity influenced by the change of core media permittivity, the thickness and permittivity of the adsorbed substance, prove that the sensitivity of the metamaterial sensor is more than 7 times that of the traditional microring resonator sensor, and the metamaterial layer loaded in the inner side of the microring doesn’t affect the high Q performance of the microring resonator. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)
Open AccessArticle A Transflective Nano-Wire Grid Polarizer Based Fiber-Optic Sensor
Sensors 2011, 11(3), 2488-2495; doi:10.3390/s110302488
Received: 9 January 2011 / Revised: 27 January 2011 / Accepted: 17 February 2011 / Published: 28 February 2011
Cited by 9 | PDF Full-text (322 KB) | HTML Full-text | XML Full-text
Abstract
A transflective nano-wire grid polarizer is fabricated on a single mode fiber tip by focused ion beam machining. In contrast to conventional absorptive in-line polarizers, the wire grids reflect TE-mode, while transmitting TM-mode light so that no light power is discarded. A [...] Read more.
A transflective nano-wire grid polarizer is fabricated on a single mode fiber tip by focused ion beam machining. In contrast to conventional absorptive in-line polarizers, the wire grids reflect TE-mode, while transmitting TM-mode light so that no light power is discarded. A reflection contrast of 13.7 dB and a transmission contrast of 4.9 dB are achieved in the 1,550 nm telecom band using a 200-nm wire grid fiber polarizer. With the help of an optic circulator, the polarization states of both the transmissive and reflective lights in the fiber may be monitored simultaneously. A kind of robust fiber optic sensor is thus proposed that could withstand light power variations. To verify the idea, a fiber pressure sensor with the sensitivity of 0.24 rad/N is demonstrated. The corresponding stress-optic coefficient of the fiber is measured. In addition to pressure sensing, this technology could be applied in detecting any polarization state change induced by magnetic fields, electric currents and so on. Full article
(This article belongs to the Special Issue Metamaterials for Sensing)

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