scholarly journals FAR FIELD IMAGING RESEARCH BASED ON MULTILAYER POSITIVE- AND NEGATIVE-REFRACTIVE-INDEX MEDIA UNDER OFF-AXIS ILLUMINATION

2009 ◽  
Vol 98 ◽  
pp. 283-298 ◽  
Author(s):  
Pengfei Cao ◽  
Xiaoping Zhang ◽  
Lin Cheng ◽  
Qingqing Meng
Keyword(s):  
Refractive Index ◽  
Negative Refractive Index ◽  
Far Field ◽  
Imaging Research ◽  
Field Imaging

Experimental far-field imaging properties of high refractive index microsphere lens

2015 ◽  
Vol 3 (6) ◽  
pp. 339 ◽  
Author(s):  
Minglei Guo ◽  
Yong-Hong Ye ◽  
Jinglei Hou ◽  
Bintao Du
Keyword(s):  
Refractive Index ◽  
High Refractive Index ◽  
Far Field ◽  
Imaging Properties ◽  
Field Imaging

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 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.

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

Compact ring resonators using negative-refractive-index microstrip line

2005 ◽  
Vol 45 (4) ◽  
pp. 294-295 ◽  
Author(s):  
Aaron D. Scher ◽  
Christopher T. Rodenbeck ◽  
Kai Chang
Keyword(s):  
Refractive Index ◽  
Microstrip Line ◽  
Negative Refractive Index ◽  
Ring Resonators ◽  
Compact Ring

scholarly journals Optical pulse dynamics in active metamaterials with positive and negative refractive index

2013 ◽  
Vol 30 (4) ◽  
pp. 1077 ◽  
Author(s):  
Alexander O. Korotkevich ◽  
Kathryn E. Rasmussen ◽  
Gregor Kovačič ◽  
Victor Roytburd ◽  
Andrei I. Maimistov ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Pulse ◽  
Negative Refractive Index ◽  
Pulse Dynamics ◽  
Active Metamaterials

scholarly journals Imaging with Local Speckle Intensity Correlations: Theory and Practice

2021 ◽  
Vol 40 (3) ◽  
pp. 1-22
Author(s):  
Marina Alterman ◽  
Chen Bar ◽  
Ioannis Gkioulekas ◽  
Anat Levin
Keyword(s):  
Near Field ◽  
Biological Tissues ◽  
Computational Imaging ◽  
Theory And Practice ◽  
Fluorescent Imaging ◽  
Light Sources ◽  
Far Field ◽  
Scattering Layer ◽  
Speckle Patterns ◽  
Field Imaging

Recent advances in computational imaging have significantly expanded our ability to image through scattering layers such as biological tissues by exploiting the auto-correlation properties of captured speckle intensity patterns. However, most experimental demonstrations of this capability focus on the far-field imaging setting, where obscured light sources are very far from the scattering layer. By contrast, medical imaging applications such as fluorescent imaging operate in the near-field imaging setting, where sources are inside the scattering layer. We provide a theoretical and experimental study of the similarities and differences between the two settings, highlighting the increased challenges posed by the near-field setting. We then draw insights from this analysis to develop a new algorithm for imaging through scattering that is tailored to the near-field setting by taking advantage of unique properties of speckle patterns formed under this setting, such as their local support. We present a theoretical analysis of the advantages of our algorithm and perform real experiments in both far-field and near-field configurations, showing an order-of magnitude expansion in both the range and the density of the obscured patterns that can be recovered.

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