scholarly journals Perfect Absorption Efficiency Circular Nanodisk Array Integrated with a Reactive Impedance Surface with High Field Enhancement

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 258 ◽  
Author(s):  
Mohamad Khoirul Anam ◽  
Sangjo Choi
Keyword(s):  
Impedance Matching ◽  
Field Enhancement ◽  
Dielectric Substrate ◽  
Absorption Efficiency ◽  
Local Surface Plasmon Resonance ◽  
Perfect Absorption ◽  
Impédance Surface ◽  
Impedance Surface ◽  
Metal Insulator Metal ◽  
Absorber Structure

Infrared (IR) absorbers based on a metal–insulator–metal (MIM) have been widely investigated due to their high absorption performance and simple structure. However, MIM absorbers based on ultrathin spacers suffer from low field enhancement. In this study, we propose a new MIM absorber structure to overcome this drawback. The proposed absorber utilizes a reactive impedance surface (RIS) to boost field enhancement without an ultrathin spacer and maintains near-perfect absorption by impedance matching with the vacuum. The RIS is a metallic patch array on a grounded dielectric substrate that can change its surface impedance, unlike conventional metallic reflectors. The final circular nanodisk array mounted on the optimum RIS offers an electric field enhancement factor of 180 with nearly perfect absorption of 98% at 230 THz. The proposed absorber exhibits robust performance even with a change in polarization of the incident wave. The RIS-integrated MIM absorber can be used to enhance the sensitivity of a local surface plasmon resonance (LSPR) sensor and surface-enhanced IR spectroscopy.

scholarly journals Impedance Enhancement of Textile Grounded Loop Antenna Using High-Impedance Surface (HIS) for Healthcare Applications

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3809
Author(s):  
Mohammed M. Bait-Suwailam ◽  
Isidoro I. Labiano ◽  
Akram Alomainy
Keyword(s):  
Impedance Matching ◽  
Loop Antenna ◽  
Healthcare Applications ◽  
Impédance Surface ◽  
Antenna Structure ◽  
Impedance Surface ◽  
High Impedance ◽  
Low Profile ◽  
Close Proximity ◽  
High Impedance Surface

In this paper, impedance matching enhancement of a grounded wearable low-profile loop antenna is investigated using a high-impedance surface (HIS) structure. The wearable loop antenna along with the HIS structure is maintained low-profile, making it a suitable candidate for healthcare applications. The paper starts with investigating, both numerically and experimentally, the effects of several textile parameters on the performance of the wearable loop antenna. The application of impedance enhancement of wearable grounded loop antenna with HIS structure is then demonstrated. Numerical full-wave simulations are presented and validated with measured results. Unlike the grounded wearable loop antenna alone with its degraded performance, the wearable loop antenna with HIS structure showed better matching performance improvement at the 2.45 GHz-band. The computed overall far-field properties of the wearable loop antenna with HIS structure shows good performance, with a maximum gain of 6.19 dBi. The effects of bending the wearable loop antenna structure with and without HIS structure as well as when in close proximity to a modeled human arm are also investigated, where good performance was achieved for the case of the wearable antenna with the HIS structure.

scholarly journals Numerical Study of an Ultra-Broadband All-Silicon Terahertz Absorber

2020 ◽  
Vol 10 (2) ◽  
pp. 436 ◽  
Author(s):  
Jinfeng Wang ◽  
Tingting Lang ◽  
Tingting Shen ◽  
Changyu Shen ◽  
Zhi Hong ◽  
...  
Keyword(s):  
Numerical Study ◽  
Structural Parameters ◽  
Impedance Matching ◽  
Single Layer ◽  
Transverse Magnetic ◽  
Absorption Efficiency ◽  
Absorption Mechanism ◽  
Loss Mechanism ◽  
Perfect Absorption ◽  
Terahertz Absorber

In this article we present and numerically investigate a broadband all-silicon terahertz (THz) absorber which consists of a single-layer periodic array of a diamond metamaterial layer placed on a silicon substrate. We simulated the absorption spectra of the absorber under different structural parameters using the commercial software Lumerical FDTD solutions, and analyzed the absorption mechanism from the distribution of the electromagnetic fields. Finally, the absorption for both transverse electric (TE) and transverse magnetic (TM) polarizations under different incident angles from 0 to 70° were investigated. Herein, electric and magnetic resonances are proposed that result in perfect broadband absorption. When the absorber meets the impedance matching principle in accordance with the loss mechanism, it can achieve a nearly perfect absorption response. The diamond absorber exhibits an absorption of ~100% at 1 THz and achieves an absorption efficiency >90% within a bandwidth of 1.3 THz. In addition, owing to the highly structural symmetry, the absorber has a polarization-independent characteristic. Compared with previous metal–dielectric–metal sandwiched absorbers, the all-silicon metamaterial absorbers can avoid the disadvantages of high ohmic losses, low melting points, and high thermal conductivity of the metal, which ensure a promising future for optical applications, including sensors, modulators, and photoelectric detection devices.

scholarly journals A Narrow-Band Multi-Resonant Metamaterial in Near-IR

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5140
Author(s):  
Farhan Ali ◽  
Serap Aksu
Keyword(s):  
Cross Sections ◽  
Narrow Band ◽  
Near Field ◽  
Impedance Matching ◽  
Perfect Absorber ◽  
Refractive Index Sensitivity ◽  
Perfect Absorption ◽  
Metal Insulator Metal ◽  
Index Sensitivity ◽  
Scattering Cross Sections

We theoretically investigate a multi-resonant plasmonic metamaterial perfect absorber operating between 600 and 950 nm wavelengths. The presented device generates 100% absorption at two resonance wavelengths and delivers an ultra-narrow band (sub-20 nm) and high quality factor (Q=44) resonance. The studied perfect absorber is a metal–insulator–metal configuration where a thin MgF2 spacer is sandwiched between an optically thick gold layer and uniformly patterned gold circular nanodisc antennas. The localized and propagating nature of the plasmonic resonances are characterized and confirmed theoretically. The origin of the perfect absorption is investigated using the impedance matching and critical coupling phenomenon. We calculate the effective impedance of the perfect absorber and confirm the matching with the free space impedance. We also investigate the scattering properties of the top antenna layer and confirm the minimized reflection at resonance wavelengths by calculating the absorption and scattering cross sections. The excitation of plasmonic resonances boost the near-field intensity by three orders of magnitude which enhances the interaction between the metamaterial surface and the incident energy. The refractive index sensitivity of the perfect absorber could go as high as S=500 nm/RIU. The presented optical characteristics make the proposed narrow-band multi-resonant perfect absorber a favorable platform for biosensing and contrast agent based bioimaging.

scholarly journals Minimized Low-Profile Wideband Antennas Using High Impedance Surface

2017 ◽  
Vol 2017 ◽  
pp. 1-12
Author(s):  
Yizhu Shen
Keyword(s):  
Radio Frequency ◽  
Low Cost ◽  
Dielectric Substrate ◽  
Impédance Surface ◽  
Impedance Surface ◽  
Antenna Size ◽  
High Impedance ◽  
Low Profile ◽  
Wireless Application ◽  
High Impedance Surface

This paper proposes minimized low-profile wideband antenna by employing high impedance surface (HIS), for wireless application scenarios at radio frequency, microwave, and even terahertz. To validate this concept with low cost and easy measurement, two prototypes at radio frequency are fabricated and tested. Firstly, antenna with dielectric-substrate reflector is proposed and analyzed and 4 × 6 HIS array is employed to minimize the antenna size to 0.57λL×0.86λL×0.078λL, while maintaining antenna performances such as bandwidth, gain, and directive radiation. Secondly, a substrate-less HIS is proposed to improve the antenna bandwidth from 36% to 52% and also reduces the antenna weight by 72%.

scholarly journals Optically Induced Field-Emission Source Based on Aligned Vertical Carbon Nanotube Arrays

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1810
Author(s):  
Mengjie Li ◽  
Qilong Wang ◽  
Ji Xu ◽  
Jian Zhang ◽  
Zhiyang Qi ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Electric Field ◽  
Field Emission ◽  
Field Enhancement ◽  
Absorption Efficiency ◽  
Photon Absorption ◽  
Nanotube Arrays ◽  
Carbon Nanotube Arrays ◽  
Induced Field ◽  
Optically Induced

Due to the high field enhancement factor and photon-absorption efficiency, carbon nanotubes (CNTs) have been widely used in optically induced field-emission as a cathode. Here, we report vertical carbon nanotube arrays (VCNTAs) that performed as high-density electron sources. A combination of high applied electric field and laser illumination made it possible to modulate the emission with laser pulses. When the bias electric field and laser power density increased, the emission process is sensitive to a power law of the laser intensity, which supports the emission mechanism of optically induced field emission followed by over-the-barrier emission. Furthermore, we determine a polarization dependence that exhibits a cosine behavior, which verifies the high possibility of optically induced field emission.

scholarly journals Hyperspectral Molecular Orientation Mapping in Metamaterials

2021 ◽  
Vol 11 (4) ◽  
pp. 1544
Author(s):  
Meguya Ryu ◽  
Yoshiaki Nishijima ◽  
Shinya Morimoto ◽  
Naoki To ◽  
Tomoki Hashizume ◽  
...  
Keyword(s):  
Molecular Orientation ◽  
Field Enhancement ◽  
Chemical Mapping ◽  
Metal Insulator ◽  
Orientation Mapping ◽  
Metal Insulator Metal ◽  
Finger Printing ◽  
Thermal Emitter ◽  
Ir Bands ◽  
Sub Wavelength

The four polarisation method is adopted for measurement of molecular orientation in dielectric nanolayers of metal-insulator-metal (MIM) metamaterials composed of gold nanodisks on polyimide and gold films. Hyperspectral mapping at the chemical finger printing spectral range of 4–20 μμm was carried out for MIM patterns of 1–2.5 μμm period (sub-wavelength). Overlay images taken at 0,π4,π2,3π4 orientation angles and subsequent baseline compensation are shown to be critically important for the interpretation of chemical mapping results and reduction of spurious artefacts. Light field enhancement in the 60-nm-thick polyimide (I in MIM) was responsible for strong absorption at the characteristic polyimide bands. Strong absorbance A at narrow IR bands can be used as a thermal emitter (emittance E=1−R), where R is the reflectance and A=1−R−T, where for optically thick samples the transmittance is T=0.

Sign in / Sign up

Export Citation Format

Share Document