Studies on Novel Hyperlens Concept for Ultrasonic Non Destructive Evaluation

2021 ◽  
Author(s):  
Pradeep Kumar ◽  
Mohamed Subair Syed Akbar Ali ◽  
Prabhu Rajagopal
Keyword(s):  
Near Field ◽  
Ultrasonic Imaging ◽  
Super Resolution ◽  
Cost Effective ◽  
Medical Diagnostics ◽  
Evanescent Waves ◽  
Far Field ◽  
Resolution Limit ◽  
Non Destructive Evaluation ◽  
Non Destructive

Abstract Ultrasonic imaging is widely preferred in the field of non-destructive evaluation, medical diagnostics, and underwater inspection because it offers various advantages such as safety and versatility. However, conventional ultrasonic imaging methods suffer from the poor resolution limit imposed by the loss of information on fine features within the near-field. Metamaterial concepts have attracted much research interest in recent years, yielding extraordinary benefits such as super-resolution imaging, vibration damping, and cloaking. In the context of imaging, Metalenses allow the successful transfer of the information carried by the evanescent waves to far-field by amplifying them and hence help in overcoming the resolution limit. Hyperlenses enable subwavelength resolution along with spatial magnification by transforming evanescent waves scattered past a material artifact into propagating waves at the far-field ‘imaging’ end of the medium. This paper discusses novel radially symmetric ultrasonic hyperlens for imaging defects in the context of non-destructive evaluation, a topic that has not been studied much. The effect of parameters such as defect extent and distance between the lens on the subwavelength imaging of the hyperlens is studied using numerical simulations. This study investigates the magnification achievable using the proposed hyperlens and the effectiveness of this approach for nondestructive evaluation using cost-effective ‘everyday’ transducers.

scholarly journals Near- to Far-Field Coupling of Evanescent Waves by Glass Microspheres

Photonics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 73
Author(s):  
Rayenne Boudoukha ◽  
Stephane Perrin ◽  
Assia Demagh ◽  
Paul Montgomery ◽  
Nacer-Eddine Demagh ◽  
...  
Keyword(s):  
Near Field ◽  
High Spatial Frequency ◽  
Super Resolution ◽  
Evanescent Waves ◽  
Whispering Gallery Modes ◽  
Far Field ◽  
Whispering Gallery ◽  
Field Coupling ◽  
Electromagnetic Simulations ◽  
Propagating Waves

Through rigorous electromagnetic simulations, the natural coupling of high-spatial-frequency evanescent waves from the near field to the far field by dielectric microspheres is studied in air. The generation of whispering gallery modes inside the microspheres is shown independently of any resonance. In addition, the conversion mechanism of these evanescent waves into propagating waves is analysed. This latter point leads to key information that allows a better physical understanding of the super-resolution phenomenon in microsphere-assisted microscopy where sub-diffraction-limit revolving power is achieved.

scholarly journals Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

2018 ◽  
Vol 9 ◽  
pp. 1536-1543 ◽  
Author(s):  
Gitanjali Kolhatkar ◽  
Alexandre Merlen ◽  
Jiawei Zhang ◽  
Chahinez Dab ◽  
Gregory Q Wallace ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Hot Spots ◽  
Near Field ◽  
Nanosphere Lithography ◽  
Plasmonic Nanostructures ◽  
Far Field ◽  
Optical Images ◽  
Spatial Frequencies ◽  
Comparison Of The Results ◽  
Non Destructive

We introduce a simple, fast, efficient and non-destructive method to study the optical near-field properties of plasmonic nanotriangles prepared by nanosphere lithography. Using a rectangular Fourier filter on the blurred signal together with filtering of the lower spatial frequencies to remove the far-field contribution, the pure near-field contributions of the optical images were extracted. We performed measurements using two excitation wavelengths (532.1 nm and 632.8 nm) and two different polarizations. After the processing of the optical images, the distribution of hot spots can be correlated with the topography of the structures, as indicated by the presence of brighter spots at the apexes of the nanostructures. This technique is validated by comparison of the results to numerical simulations, where agreement is obtained, thereby confirming the near-field nature of the images. Our approach does not require any advanced equipment and we suggest that it could be applied to any type of sample, while keeping the measurement times reasonably short.

Super-Resolution Readout for Magneto-Optical Disk by Optimizing the Deposition Condition of Non-Magnetic Mask Layer

2001 ◽  
Vol 674 ◽  
Author(s):  
Takayuki Shima ◽  
Johoo Kim ◽  
Hiroshi Fuji ◽  
Nobufumi Atoda ◽  
Junji Tominaga
Keyword(s):  
Silver Oxide ◽  
Near Field ◽  
Numerical Aperture ◽  
Super Resolution ◽  
Laser Wavelength ◽  
Deposition Condition ◽  
Resolution Limit ◽  
Plasma Sputtering ◽  
Mask Layer ◽  
Disk Structure

ABSTRACTSuper-resolution near-field structure (Super-RENS) was prepared by a heliconwave-plasma sputtering method to improve the disk property that is combined with a magneto-optical (MO) recording disk. Antimony and silver-oxide mask layers were prepared by the method and refractive indices were measured. Recording and retrieving of signals beyond the resolution limit (<370 nm) were achieved for both mask cases. Attempts to optimize the disk structure were also made using a conventional sputtering method. The smallest mark size was around 200 nm and the highest carrier-to-noise ratio (CNR) was 30 dB for 300-nm mark and 22 dB for 250-nm, when using a laser wavelength of 780 nm and a numerical aperture of 0.53. We have found that there is a competing super-resolutional mechanism besides Super-RENS that appears when high readout laser power is applied. This mechanism played rather an important role at least in the mark-size range of 200-370 nm.

scholarly journals Progress towards the realization of an optical Far-Field Superlens

2021 ◽  
Author(s):  
◽  
Farzaneh Fadakar Masouleh
Keyword(s):  
Zinc Oxide ◽  
Near Field ◽  
Diffraction Gratings ◽  
Evanescent Waves ◽  
Field Pattern ◽  
Far Field ◽  
Potential Candidate ◽  
Plasmonic Material ◽  
Far Field Pattern ◽  
The Impact

<p>Conventional optics suffer from a fundamental resolution limit due to the nature of light. The near-field superlens concept was introduced two decades ago, and its theory for enabling high resolution imaging is well-established now. Initially, this superlens, which has a simple setup, became a hot topic given the proposition of overcoming the diffraction limit. It has been demonstrated that a near-field superlens can reconstruct images using evanescent waves emanating from small objects by means of resonant excitations on the surface of the superlens. A modified version of the superlens named the far-field superlens is theorized to be able to project the near-field subwavelength information to the far-field region. By design, the far-field superlens is a near-field superlens with nanostructures added on top of it. These nanostructures, referred to as diffraction gratings help couple object information available in the evanescent waves to the far-field. Work reported in this thesis is divided to two major sections. The first describes the modelling technique that investigates the performance of a far-field superlens. This section focuses on evaluating the impact of the diffraction gratings geometry and the object size on the far-field superlens performance as well as the resulting far-field pattern. It was shown that a far-field superlens with a nanograting having a duty cycle of 40% to 50% produces the maximum intensity and contrast in the far-field interactions. For periodic rectangular objects, an inverse-trapezoidal nanograting was shown to provide the best contrast and intensity for far-field interactions. The minimal simulation domain to model a symmetric far-field superlens design was determined both in 2D and 3D. This input reduced the required modelling time and resources. Finally, a 3D far-field superlens model was proposed, and the effect of light polarization on the far-field pattern was studied. The second section of this thesis contains the experimental study that explores a new material as a potential candidate for the construction of far-field superlens. The material conventionally used for superlens design is silver, as its plasmonic properties are well-established. However, scaling down silver features to the nanoscale introduces fundamental fabrication challenges. Furthermore, silver oxidizes due to its reactions with sulphur compounds at ambient conditions, which means that operating a silver far-field superlens is only possible in a well-controlled environment. This disagrees with our proposed concept of a low-cost and robust superlens imaging device. On the other hand, highly doped semiconductors are emerging candidates for plasmonic applications due to the possibility of tuning their optical and electrical properties during the fabrication process. While the working principle of a superlens is independent of the plasmonic material of choice, every plasmonic material has a particular range of operating wavelengths. The pros and cons of each plasmonic material are usually identified once used experimentally. In this work, aluminium-doped zinc oxide was the proposed material of choice for the far-field superlens design. The second part of this thesis details the characterization results of the optical, electrical and structural properties of this proposed alternative. Our aluminium-doped zinc oxide samples were highly transparent for large parts of the spectrum. Their carrier concentration was of the order of 10+20 cm-3, and a resistivity of about 10-3 Ω.cm was achieved. The modelled dielectric permittivity for the studied samples showed a cross-over frequency in the near-infrared region, with the highest plasma frequency achieved in this study being 4710 cm-1.</p>

Hydraulic Fracturing Diagnostics Utilizing Near and Far-Field Distributed Acoustic Sensing DAS Data Correspondences

2021 ◽  
Author(s):  
Yinghui Wu ◽  
Robert Hull ◽  
Andrew Tucker ◽  
Craig Rice ◽  
Peter Richter ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Near Field ◽  
Fracture Propagation ◽  
Cost Effective ◽  
Hydraulic Fractures ◽  
Far Field ◽  
Distributed Temperature Sensing ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing ◽  
Multiple Fibers

Abstract Distributed fiber-optic sensing (DFOS) has been utilized in unconventional reservoirs for hydraulic fracture efficiency diagnostics for many years. Downhole fiber cables can be permanently installed external to the casing to monitor and measure the uniformity and efficiency of individual clusters and stages during the completion in the near-field wellbore environment. Ideally, a second fiber or multiple fibers can be deployed in offset well(s) to monitor and characterize fracture geometries recorded by fracture-driven interactions or frac-hits in the far-field. Fracture opening and closing, stress shadow creation and relaxation, along with stage isolation can be clearly identified. Most importantly, fracture propagation from the near to far-field can be better understood and correlated. With our current technology, we can deploy cost effective retrievable fibers to record these far-field data. Our objective here is to highlight key data that can be gathered with multiple fibers in a carefully planned well-spacing study and to evaluate and understand the correspondence between far-field and near-field Distributed Acoustic Sensing (DAS) data. In this paper, we present a case study of three adjacent horizontal wells equipped with fiber in the Permian basin. We can correlate the near-field fluid allocation across a stage down to the cluster level to far-field fracture driven interactions (FDIs) with their frac-hit strain intensity. With multiple fibers we can evaluate fracture geometry, the propagation of the hydraulic fractures, changes in the deformation related to completion designs, fracture complexity characterization and then integrate the results with other data to better understand the geomechanical processes between wells. Novel frac-hit corridor (FHC) is introduced to evaluate stage isolation, azimuth, and frac-hit intensity (FHI), which is measured in far-field. Frac design can be evaluated with the correlation from near-field allocation to far-field FHC and FHI. By analyzing multiple treatment and monitor wells, the correspondence can be further calibrated and examined. We observe the far-field FHC and FHI are directly related to the activities of near-field clusters and stages. A leaking plug may directly result in FHC overlapping, gaps and variations in FHI, which also can be correlated to cluster uniformity. A near-far field correspondence can be established to evaluate FHC and FHI behaviors. By utilizing various completion designs and related measurements (e.g. Distributed Temperature Sensing (DTS), gauges, microseismic etc.), optimization can be performed to change the frac design based on far-field and near-field DFOS data based on the Decision Tree Method (DTM). In summary, hydraulic fracture propagation can be better characterized, measured, and understood by deploying multiple fibers across a lease. The correspondence between the far-field measured FHC and FHI can be utilized for completion evaluation and diagnostics. As the observed strain is directly measured, completion engineering and geoscience teams can confidently optimize their understanding of the fracture designs in real-time.

scholarly journals Demonstration of nanoimprinted hyperlens array for high-throughput sub-diffraction imaging

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Minseop Byun ◽  
Dasol Lee ◽  
Minkyung Kim ◽  
Yangdoo Kim ◽  
Kwan Kim ◽  
...  
Keyword(s):  
Real Time ◽  
Large Scale ◽  
Medical Science ◽  
Super Resolution ◽  
Fabrication Process ◽  
Far Field ◽  
Resolution Limit ◽  
Imaging Science ◽  
Diffraction Imaging ◽  
Resolution Imaging

Abstract Overcoming the resolution limit of conventional optics is regarded as the most important issue in optical imaging science and technology. Although hyperlenses, super-resolution imaging devices based on highly anisotropic dispersion relations that allow the access of high-wavevector components, have recently achieved far-field sub-diffraction imaging in real-time, the previously demonstrated devices have suffered from the extreme difficulties of both the fabrication process and the non-artificial objects placement. This results in restrictions on the practical applications of the hyperlens devices. While implementing large-scale hyperlens arrays in conventional microscopy is desirable to solve such issues, it has not been feasible to fabricate such large-scale hyperlens array with the previously used nanofabrication methods. Here, we suggest a scalable and reliable fabrication process of a large-scale hyperlens device based on direct pattern transfer techniques. We fabricate a 5 cm × 5 cm size hyperlenses array and experimentally demonstrate that it can resolve sub-diffraction features down to 160 nm under 410 nm wavelength visible light. The array-based hyperlens device will provide a simple solution for much more practical far-field and real-time super-resolution imaging which can be widely used in optics, biology, medical science, nanotechnology and other closely related interdisciplinary fields.

Far-field super-resolution imaging using near-field illumination by micro-fiber

2013 ◽  
Vol 102 (1) ◽  
pp. 013104 ◽  
Author(s):  
Xiang Hao ◽  
Xu Liu ◽  
Cuifang Kuang ◽  
Yanghui Li ◽  
Yulong Ku ◽  
...  
Keyword(s):  
Near Field ◽  
Super Resolution ◽  
Far Field ◽  
Resolution Imaging

Near-Field Scanning Optical Microscopy

1987 ◽  
Vol 45 ◽  
pp. 184-187
Author(s):  
E. Betzig ◽  
M. Isaacson ◽  
A. Lewis ◽  
K. Lin
Keyword(s):  
Spatial Resolution ◽  
Structural Damage ◽  
Near Field ◽  
Far Field ◽  
Resolution Limit ◽  
Field Methods ◽  
General Applicability ◽  
Minimal Sample ◽  
Near Field Imaging ◽  
Field Imaging

The spatial resolution of most of the imaging or microcharacterization methods presently in use are fundamentally limited by the wavelength of the exciting or the emitted radiation being used. In general, the smaller the wavelength of the exciting probe, the greater the structural damage to the sample under study. Thus, the requirements of minimal sample alteration and high spatial resolution seem to be at odds with one another.However, the reason for this wavelength resolution limit is due to the far field methods for producing or detecting the radiation of interest. If one does not use far field optics, but rather the method of near field imaging, the spatial resolution attainable can be much smaller than the wavelength of the radiation used. This method of near field imaging has a general applicability for all wave probes.

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