scholarly journals Negative Index Metamaterial Lens for Subwavelength Microwave Detection

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4782
Author(s):  
Srijan Datta ◽  
Saptarshi Mukherjee ◽  
Xiaodong Shi ◽  
Mahmood Haq ◽  
Yiming Deng ◽  
...  
Keyword(s):  
Refractive Index ◽  
Periodic Structures ◽  
Negative Refractive Index ◽  
Far Field ◽  
Lens Design ◽  
Theoretical Formulation ◽  
System A ◽  
Numerical Studies ◽  
Naturally Occurring

Metamaterials are engineered periodic structures designed to have unique properties not encountered in naturally occurring materials. One such unusual property of metamaterials is the ability to exhibit negative refractive index over a prescribed range of frequencies. A lens made of negative refractive index metamaterials can achieve resolution beyond the diffraction limit. This paper presents the design of a metamaterial lens and its use in far-field microwave imaging for subwavelength defect detection in nondestructive evaluation (NDE). Theoretical formulation and numerical studies of the metamaterial lens design are presented followed by experimental demonstration and characterization of metamaterial behavior. Finally, a microwave homodyne receiver-based system is used in conjunction with the metamaterial lens to develop a far-field microwave NDE sensor system. A subwavelength focal spot of size 0.82λ was obtained. The system is shown to be sensitive to a defect of size 0.17λ × 0.06λ in a Teflon sample. Consecutive positions of the defect with a separation of 0.23λ was resolvable using the proposed system.

Negative Refractive Index in a Two-Dimensional Nonlinear Rotator Lattice

2021 ◽  
Author(s):  
Lezheng Fang ◽  
Michael J. Leamy
Keyword(s):  
Numerical Simulation ◽  
Refractive Index ◽  
Direct Numerical Simulation ◽  
Incident Wave ◽  
Wave Amplitude ◽  
Multiple Scales ◽  
Negative Refractive Index ◽  
Index Of Refraction ◽  
Far Field ◽  
Negative Index

Abstract Acoustic metamaterials achieving negative index refraction usually operate linearly over a narrowband of frequency and consist of complex unit cell structures incorporating resonators. In this paper, we propose and analyze a simple, non-resonant, nonlinear rotator lattice structure which can be configured with either a positive or negative index of refraction over a broadband frequency range. The system’s frequency-dependent transmission is studied analytically via a reduced model along the interface of positive and negative refractive index lattices. Results for energy transmission are compared to those obtained using direct numerical simulation and close agreement is documented for small amplitude waves. For larger amplitude waves, a multiple scales analysis approach is used to show that the nonlinearity of the lattice shifts the system’s band structure, inducing amplitude-dependent transmission. For the studied system, the transmission decreases as we increase the incident wave amplitude, agreeing qualitatively with results from direct numerical simulation. At large-enough amplitudes, near the interface the wave amplitude decreases rapidly. As the wave travels further into the media, the amplitude drops, causing the nonlinear effect to decline as well. This decaying envelope does not result in a zero transmission in the far field, as expected from linear theory, and instead, the nonlinearity of the proposed rotator lattice prevents the far-field transmitted wave from surpassing a specific threshold amplitude, regardless of the incident wave. This finding may serve as an inspiration for designing nonlinear wave saturators.

scholarly journals Homogeneous Hyperbolic Systems for Terahertz and Far-Infrared Frequencies

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Leonid V. Alekseyev ◽  
Viktor A. Podolskiy ◽  
Evgenii E. Narimanov
Keyword(s):  
Refractive Index ◽  
Negative Refractive Index ◽  
Hyperbolic Systems ◽  
Far Infrared ◽  
Low Loss ◽  
Naturally Occurring ◽  
Ir Frequencies ◽  
Index Systems ◽  
Infrared Frequencies

We demonstrate that homogeneous naturally-occurring materials can form hyperbolic media, and can be used for nonmagnetic negative refractive index systems. We present specific realizations of the proposed approach for the THz and far-IR frequencies. The proposed structures operate away from resonance, thereby promising the capacity for low-loss devices.

Acoustic far-field focusing effect for two-dimensional graded negative refractive-index sonic crystals

2010 ◽  
Vol 96 (26) ◽  
pp. 263502 ◽  
Author(s):  
Shasha Peng ◽  
Zhaojian He ◽  
Han Jia ◽  
Anqi Zhang ◽  
Chunyin Qiu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Negative Refractive Index ◽  
Far Field ◽  
Two Dimensional ◽  
Focusing Effect ◽  
Sonic Crystals

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

TEM characterization of proton-exchanged LiNbO3 optical waveguides

1986 ◽  
Vol 44 ◽  
pp. 480-481
Author(s):  
W. E. Lee
Keyword(s):  
Refractive Index ◽  
Benzoic Acid ◽  
Optical Waveguides ◽  
Total Internal Reflection ◽  
Index Of Refraction ◽  
Optical Measurements ◽  
Lithium Ions ◽  
Wide Channel ◽  
Tem Characterization

An optical waveguide consists of a several-micron wide channel with a slightly different index of refraction than the host substrate; light can be trapped in the channel by total internal reflection.Optical waveguides can be formed from single-crystal LiNbO3 using the proton exhange technique. In this technique, polished specimens are masked with polycrystal1ine chromium in such a way as to leave 3-13 μm wide channels. These are held in benzoic acid at 249°C for 5 minutes allowing protons to exchange for lithium ions within the channels causing an increase in the refractive index of the channel and creating the waveguide. Unfortunately, optical measurements often reveal a loss in waveguiding ability up to several weeks after exchange.

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