scholarly journals Manipulating guided wave radiation with integrated geometric metasurface

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Bin Fang ◽  
Zhizhang Wang ◽  
Shenglun Gao ◽  
Shining Zhu ◽  
Tao Li
Keyword(s):  
Free Space ◽  
Guided Waves ◽  
Guided Wave ◽  
Optical Systems ◽  
Wave Radiation ◽  
Optical Antennas ◽  
Integrated Devices ◽  
Unit Cells ◽  
New Perspective ◽  
On Chip

Abstract Metasurfaces have manifested unprecedented capabilities in manipulating light by subwavelength unit cells, facilitating the miniaturization and multifunctions of optical systems. On the other hand, lithium niobate on insulator (LNOI) technology is revolutionizing the integrated photonics, enabling multifunctional devices and applications. Yet the optical interface for coupling and manipulation is not sufficient and versatile. Here, we developed a geometric metasurface interface for LNOI waveguide and demonstrated several on-chip integrated devices for free space light field manipulations. By decorating waveguides with subwavelength optical antennas, we manipulated the guided waves into desired wavefronts in space, achieved complex free-space functions, such as focusing, multichannel vortex beam generation, and holography. Our architecture goes beyond the conventional gratings and enriches the functionalities of metasurface, which would open up a new perspective for future versatile guided-wave driven optical devices.

scholarly journals Molding free-space light with guided wave–driven metasurfaces

2020 ◽  
Vol 6 (29) ◽  
pp. eabb4142
Author(s):  
Xuexue Guo ◽  
Yimin Ding ◽  
Xi Chen ◽  
Yao Duan ◽  
Xingjie Ni
Keyword(s):  
Free Space ◽  
Guided Waves ◽  
Guided Wave ◽  
Microring Resonator ◽  
Beam Deflection ◽  
Integrated Photonics ◽  
Complete Control ◽  
Integrated Devices ◽  
Out Of Plane ◽  
On Chip

Metasurfaces with unparalleled controllability of light have shown great potential to revolutionize conventional optics. However, they mainly require external light excitation, which makes it difficult to fully integrate them on-chip. On the other hand, integrated photonics enables packing optical components densely on a chip, but it has limited free-space light controllability. Here, by dressing metasurfaces onto waveguides, we molded guided waves into any desired free-space modes to achieve complex free-space functions, such as out-of-plane beam deflection and focusing. This metasurface also breaks the degeneracy of clockwise- and counterclockwise-propagating whispering gallery modes in an active microring resonator, leading to on-chip direct orbital angular momentum lasing. Our study shows a viable route toward complete control of light across integrated photonics and free-space platforms and paves a way for creating multifunctional photonic integrated devices with agile access to free space, which enables a plethora of applications in communications, remote sensing, displays, etc.

scholarly journals Topologically protected broadband rerouting of propagating waves around complex objects

Nanophotonics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 1371-1378 ◽  
Author(s):  
Zeki Hayran ◽  
Seyyed Ali Hassani Gangaraj ◽  
Francesco Monticone
Keyword(s):  
Free Space ◽  
Electromagnetic Waves ◽  
Guided Waves ◽  
Plane Waves ◽  
Transmission Efficiency ◽  
Wave Radiation ◽  
Isotropic Layer ◽  
Complex Objects ◽  
Plasmonic Material ◽  
Propagating Waves

AbstractAchieving robust propagation and guiding of electromagnetic waves through complex and disordered structures is a major goal of modern photonics research, for both classical and quantum applications. Although the realization of backscattering-free and disorder-immune guided waves has recently become possible through various photonic schemes inspired by topological insulators in condensed matter physics, the interaction between such topologically protected guided waves and free-space propagating waves remains mostly unexplored, especially in the context of scattering systems. Here, we theoretically demonstrate that free-space propagating plane waves can be efficiently coupled into topological one-way surface waves, which can seamlessly flow around sharp corners and electrically large barriers and release their energy back into free space in the form of leaky-wave radiation. We exploit this physical mechanism to realize topologically protected wave-rerouting around an electrically large impenetrable object of complex shape, with transmission efficiency exceeding 90%, over a relatively broad bandwidth. The proposed topological wave-rerouting scheme is based on a stratified structure composed of a topologically nontrivial magnetized plasmonic material coated by a suitable isotropic layer. Our results may open a new avenue in the field of topological photonics and electromagnetics, for applications that require engineered interactions between guided waves and free-space propagating waves, including for complex beam-routing systems and advanced stealth technology. More generally, our work may pave the way for robust defect/damage-immune scattering and radiating systems.

Stress evaluation in seven-wire strands based on singular value feature of ultrasonic guided waves

2021 ◽  
pp. 147592172110053
Author(s):  
Qian Ji ◽  
Li Jian-Bin ◽  
Liu Fan-Rui ◽  
Zhou Jian-Ting ◽  
Wang Xu
Keyword(s):  
Dispersion Curve ◽  
Support Vector Regression ◽  
Stress Level ◽  
Guided Waves ◽  
Guided Wave ◽  
Singular Value ◽  
Support Vector ◽  
Support Vector Regression Model ◽  
Various Boundary Conditions ◽  
Wave Methods

The seven-wire strands are the crucial components of prestressed structures, though their performance inevitably degrades with the passage of time. The ultrasonic guided wave methods have been intensely studied, owing to its tremendous potential for full-scale applications, among the existing nondestructive testing methods, for evaluating the stress status of strands. We have employed the theoretical and finite element methods to solve the dispersion curve of single wire and steel strands under various boundary conditions. Thereafter, the singular value decomposition was adopted to work with the simulated and experimental signals for extracting a feature vector that carries valuable stress status information. The effectiveness of the vector was verified by analyzing the relationship between the vector and the stress level. The vector was also used as an input to establish a support vector regression model. The accuracy of the model has been discussed for different sample sizes. The results show that the fundamental mode dispersion curve offset on the high-frequency part and cut-off frequency increases as the boundary constraints enhance. Simulated and experimental results have demonstrated the effectiveness and potential of the proposed support vector regression method for evaluating the stress level in the strands. This method performs well even at low stress levels and the reliability can be enhanced by adding more samples.

scholarly journals Towards lab-on-chip ultrasensitive ethanol detection using photonic crystal waveguide operating in the mid infrared

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Rostamian ◽  
Ehsan Madadi-Kandjani ◽  
Hamed Dalir ◽  
Volker J. Sorger ◽  
Ray T. Chen
Keyword(s):  
Photonic Crystal ◽  
Slow Light ◽  
High Sensitivity ◽  
Guided Wave ◽  
Silicon On Insulator ◽  
Group Index ◽  
Photonic Crystal Waveguide ◽  
Mid Infrared ◽  
Lab On Chip ◽  
On Chip

Abstract Thanks to the unique molecular fingerprints in the mid-infrared spectral region, absorption spectroscopy in this regime has attracted widespread attention in recent years. Contrary to commercially available infrared spectrometers, which are limited by being bulky and cost-intensive, laboratory-on-chip infrared spectrometers can offer sensor advancements including raw sensing performance in addition to use such as enhanced portability. Several platforms have been proposed in the past for on-chip ethanol detection. However, selective sensing with high sensitivity at room temperature has remained a challenge. Here, we experimentally demonstrate an on-chip ethyl alcohol sensor based on a holey photonic crystal waveguide on silicon on insulator-based photonics sensing platform offering an enhanced photoabsorption thus improving sensitivity. This is achieved by designing and engineering an optical slow-light mode with a high group-index of n g  = 73 and a strong localization of modal power in analyte, enabled by the photonic crystal waveguide structure. This approach includes a codesign paradigm that uniquely features an increased effective path length traversed by the guided wave through the to-be-sensed gas analyte. This PIC-based lab-on-chip sensor is exemplary, spectrally designed to operate at the center wavelength of 3.4 μm to match the peak absorbance for ethanol. However, the slow-light enhancement concept is universal offering to cover a wide design-window and spectral ranges towards sensing a plurality of gas species. Using the holey photonic crystal waveguide, we demonstrate the capability of achieving parts per billion levels of gas detection precision. High sensitivity combined with tailorable spectral range along with a compact form-factor enables a new class of portable photonic sensor platforms when combined with integrated with quantum cascade laser and detectors.

scholarly journals Laser-excited elastic guided waves reveal the complex mechanics of nanoporous silicon

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Marc Thelen ◽  
Nicolas Bochud ◽  
Manuel Brinker ◽  
Claire Prada ◽  
Patrick Huber
Keyword(s):  
Guided Waves ◽  
Laser Ultrasonics ◽  
Bulk Silicon ◽  
Nanoporous Silicon ◽  
Stiffness Reduction ◽  
Mechanical Characterisation ◽  
Isotropic Elasticity ◽  
On Chip ◽  
Non Destructive

AbstractNanoporosity in silicon leads to completely new functionalities of this mainstream semiconductor. A difficult to assess mechanics has however significantly limited its application in fields ranging from nanofluidics and biosensorics to drug delivery, energy storage and photonics. Here, we present a study on laser-excited elastic guided waves detected contactless and non-destructively in dry and liquid-infused single-crystalline porous silicon. These experiments reveal that the self-organised formation of 100 billions of parallel nanopores per square centimetre cross section results in a nearly isotropic elasticity perpendicular to the pore axes and an 80% effective stiffness reduction, altogether leading to significant deviations from the cubic anisotropy observed in bulk silicon. Our thorough assessment of the wafer-scale mechanics of nanoporous silicon provides the base for predictive applications in robust on-chip devices and evidences that recent breakthroughs in laser ultrasonics open up entirely new frontiers for in-situ, non-destructive mechanical characterisation of dry and liquid-functionalised porous materials.

Ultrasonic unilateral double-position excitation lamb wave defect detection and quantification method for ground electrode of transmission tower

2021 ◽  
pp. 1-15
Author(s):  
Kuan Ye ◽  
Kai Zhou ◽  
Ren Zhigang ◽  
Ruizhe Zhang ◽  
Chunsheng Li ◽  
...  
Keyword(s):  
Guided Waves ◽  
Power Transmission ◽  
Geometric Model ◽  
Guided Wave ◽  
Quantization Error ◽  
Dispersion Function ◽  
Stable Operation ◽  
Transmission Tower ◽  
Ultrasonic Guided Wave ◽  
Transmission Towers

The power transmission tower’s ground electrode defect will affect its normal current dispersion function and threaten the power system’s safe and stable operation and even personal safety. Aiming at the problem that the buried grounding grid is difficult to be detected, this paper proposes a method for identifying the ground electrode defects of transmission towers based on single-side multi-point excited ultrasonic guided waves. The geometric model, ultrasonic excitation model, and physical model are established, and the feasibility of ultrasonic guided wave detection is verified through the simulation and experiment. In actual inspection, it is equally important to determine the specific location of the defect. Therefore, a multi-point excitation method is proposed to determine the defect’s actual position by combining the ultrasonic guided wave signals at different excitation positions. Besides, the precise quantification of flat steel grounding electrode defects is achieved through the feature extraction-neural network method. Field test results show that, compared with the commercial double-sided excitation transducer, the single-sided excitation transducer proposed in this paper has a lower defect quantization error in defect quantification. The average quantization error is reduced by approximately 76%.

scholarly journals Longitudinal Guided Wave Inspection of Small-Diameter Elbowed Steel Tubes with a Novel Squirrel-Cage Magnetostrictive Sensor

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Yao Liu ◽  
Xiucheng Liu ◽  
Chehua Yang ◽  
Wenxin Guo ◽  
Bin Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Guided Waves ◽  
Mode Conversion ◽  
Small Diameter ◽  
Longitudinal Mode ◽  
Guided Wave ◽  
Wall Defect ◽  
Squirrel Cage ◽  
Simulation Results ◽  
Magnetostrictive Sensor

In the study, ultrasonic longitudinal mode guided waves were employed to detect defects in elbowed tubes (without welds) with a diameter of 10 mm. Finite element simulation results highlighted that the emitted L(0,1) mode guided waves experienced strong reflection and mode conversion at the elbow region to generate F(1,1) mode, followed by slow and weak F(2,1) mode. The guided wave reflected from the elbow with a through-wall defect was manifested as two overlapped wave packets, which were good indicators of a defective elbow. To conduct L(0,1) mode guided waves inspection on the small-diameter elbowed tubes, a novel tailored squirrel-cage magnetostrictive sensor was employed in the experiment. The new sensor employed the configuration of segmental iron-cobalt strips and small-size permanent magnet arrays. The entire sensor is composed of two identical C-shaped sensor elements and can be recycled and installed conveniently. Experimental results obtained from healthy and defective tubes were consistent with the conclusions obtained from finite element simulations. An artificial through-wall defect at the elbow and a notch defect at the straight part of the tube could be simultaneously detected by L(0,1) mode guided waves through comparing experimental signals with simulation results.

Guided Wave Focusing Mechanics in Pipe

2003 ◽  
Author(s):  
Takahiro Hayashi ◽  
Koichiro Kawashima ◽  
Zongqi Sun ◽  
Joseph L. Rose
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Guided Waves ◽  
Wave Structure ◽  
Guided Wave ◽  
Pipe Inspection ◽  
Specific Point ◽  
Wave Focusing ◽  
Beam Focusing ◽  
Subsequent Time

Guided waves can be used in pipe inspection over long distances. Presented in this paper is a beam focusing technique to improve the S/N ratio of the reflection from a tiny defect. Focusing is accomplished by using non-axisymmetric waveforms and subsequent time delayed superposition at a specific point in a pipe. A semi-analytical finite element method is used to present wave structure in the pipe. Focusing potential is also studied with various modes and frequencies.

scholarly journals Rail Diagnostics Based on Ultrasonic Guided Waves: An Overview

2021 ◽  
Vol 11 (3) ◽  
pp. 1071
Author(s):  
Davide Bombarda ◽  
Giorgio Matteo Vitetta ◽  
Giovanni Ferrante
Keyword(s):  
Guided Waves ◽  
Structural Integrity ◽  
Diagnostic Procedures ◽  
Guided Wave ◽  
Rolling Stock ◽  
Technical Literature ◽  
Track Maintenance ◽  
Rail Network ◽  
Ultrasonic Guided Wave ◽  
Maintenance And Inspection

Rail tracks undergo massive stresses that can affect their structural integrity and produce rail breakage. The last phenomenon represents a serious concern for railway management authorities, since it may cause derailments and, consequently, losses of rolling stock material and lives. Therefore, the activities of track maintenance and inspection are of paramount importance. In recent years, the use of various technologies for monitoring rails and the detection of their defects has been investigated; however, despite the important progresses in this field, substantial research efforts are still required to achieve higher scanning speeds and improve the reliability of diagnostic procedures. It is expected that, in the near future, an important role in track maintenance and inspection will be played by the ultrasonic guided wave technology. In this manuscript, its use in rail track monitoring is investigated in detail; moreover, both of the main strategies investigated in the technical literature are taken into consideration. The first strategy consists of the installation of the monitoring instrumentation on board a moving test vehicle that scans the track below while running. The second strategy, instead, is based on distributing the instrumentation throughout the entire rail network, so that continuous monitoring in quasi-real-time can be obtained. In our analysis of the proposed solutions, the prototypes and the employed methods are described.

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