Diffraction Phenomena Research Articles

Four-level diffractive photon sieves by deep-UV femtosecond laser ablation

A growing demand for complex light manipulation and miniaturization of optics necessitates advanced optical elements, operating on light diffraction phenomena, capable not only of reshaping the intensity distribution but also integrating many optical functions in a compact, durable device. The prevailing fabrication methods for these elements often involve multi-step lithographic processes. In contrast, direct laser ablation offers a single-step, cost-effective, and maskless alternative. However, using solid-state laser systems’ fundamental wavelength (in the IR range) for ablation lacks the precise depth control required for multi-level diffractive optical element fabrication. In this paper, we present the first experimental proof that femtosecond direct laser ablation in the UV spectral range is a reliable method for fabricating diffractive optical elements. We demonstrate the high-quality production of compact photon sieve focusing elements with the shortest focal length ever reported at 9 mm. Furthermore, we report an efficiency of 3.3%, which, to our knowledge, is the highest for elements with such a small focal length and not far from the theoretical efficiency limit of 4.46% (considering perfect cylindrical ablated pits). Moreover, our fabricated elements focus light to a 2.3% smaller focal spot if compared to the refractive lens with the same parameters. This fabrication method shows great promise for advanced applications that require precise depth control in wide band gap materials, such as the fused quartz used in this study.

Observation of Young’s double-slit phenomenon in anti-PT-symmetric electrical circuits

Abstract In the last few decades, interference has been extensively studied in both the quantum and classical fields, which reveals light volatility and is widely used for high-precision measurements. We have put forward the phenomenon in which the discrete diffraction and interference phenomena, presented by the time-varying voltage of a Su-Schrieffer-Heeger (SSH) circuit model with an anti-PT (APT) symmetry. To demonstrate Young’s double-slit phenomenon in an APT circuit, we initially explore the coupled mode theory (CMT) of voltage in the broken phase, observe discrete diffraction under single excitation and interference under double excitations. Furthermore, we design a phase-shifting circuit to observe the effects of phase difference and distance on discrete interference. Our work combines the effects in optics with condensed matter physics, show the Young’s double-slit phenomenon in electrical circuits theoretically and experimentally.

Optical Disc Structures and Diffraction Patterns: Theoretical Foundations and Experimental Applications

Abstract This investigation advances the experimental exploration of optical discs' diffraction phenomena, meticulously constructing optical pathways to ascertain the track pitch within the disc employing both transmission and reflection grating paradigms. Furthermore, this study devises a novel apparatus and methodology for the precise measurement of optical wavelengths, aiming to elucidate the intricate diffraction patterns and the underlying mechanisms of optical discs' structure. This endeavor not only validates the methodological soundness and efficacy of the proposed approach but also pioneers new avenues for research into physics experiments leveraging optical discs. The application of optical discs in educational settings transcends traditional experimental pedagogy, fostering students' capabilities to independently conceptualize experiments and delve into scientific explorations.

TXRF capability of metallic contamination analysis on rough silicon wafers

AbstractTotal X-Ray Fluorescence (TXRF) is a non-destructive technique for the characterization of metallic contaminants on bare silicon wafers. TXRF is sensible to roughness leading to a diffraction phenomenon. In this study, the effects of roughness on TXRF analysis were evaluated with various rough silicon wafers produced by microelectronic processes of grinding, wet cleaning and chemical mechanical polishing. TXRF parameters rise as roughness increases, starting from 3 nm RMS (Root Mean Square) roughness. On spectra, characteristic Si (silicon wafer) and W (TXRF anode) peaks widen. Secondary peaks, sum/escape peaks appear, inducing interferences with Al, Cu, Zn and background noise increases as well. Through intentionally contaminated grinded wafers (RMS 12 nm) by spin-coating at selected concentrations, it was observed that most of the elements are quantified at 1 × 1012 at/cm2. At concentrations of 1 × 1010 at/cm2 and 1 × 1011 at/cm2, only few elements are quantified due to the elevated background noise and interferences. Graphical abstract

A comprehensive unsteady RANS numerical investigation to unveil the influence of wave steepness on the motion dynamics and added resistance of a ship in waves

In this study, we investigate the influence of wave steepness on both ship motions and added resistance in regular head waves by conducting simulations at three distinct wave steepness levels using unsteady RANS method. Numerical results show that, when wavelength comparable to the ship length, the interaction of body nonlinearity and wave nonlinearity results in highly nonlinear behavior in the time history of added resistance. The study illustrates, step-by-step, the hydrodynamic pressure distribution on the hull during an encounter period, highlighting the time-varying nature of the added resistance. Examining the visualised results, it is observed that in certain instances, high pressure may be exerted on the flat bottom of the trimmed ship and contribute significantly to the added resistance. It is observed that, when wavelength is comparable to ship length, the added resistance coefficient decreases with increasing wave steepness. Specifically, at λ/LPP = 1.15, |CAW,H/λ=1/30−CAW,H/λ=1/60|CAW,H/λ=1/60 = 27.1%. In relatively short waves the diffraction phenomena dominate and the resulting added resistance exhibits limited nonlinearity. However, obtaining stable results in such cases proves challenging. Finally, the influence of wave steepness on added resistance is quantified. The results are useful for improving the transparent methods for predicting the added resistance in wave.

Nanofluidic Detection Platform for Simultaneous Light Absorption and Scattering Measurement of Individual Nanoparticles in Flow.

Characterization and quantification of plasmonic nanoparticles at the single particle level have become increasingly important with the advancements in nanotechnology and their application to various biological analyses including diagnostics, photothermal therapy, and immunoassays. While various nanoparticle detection methodologies have been developed and widely used, simultaneous measurement of light absorption and scattering from individual plasmonic nanoparticles in flow is still challenging. Herein, we describe a novel nanofluidic detection platform that enables simultaneous measurement of absorption and scattering signals from individual nanoparticles within a nanochannel. Our detection platform utilized optical diffraction phenomena by a single nanochannel as both a readout signal for photothermal detection and a reference light for interferometric scattering detection. Through the elucidation of the frequency effect on the detection performance and optimization of experimental conditions, we achieved the classification of gold and silver nanoparticles with a diameter of 20-60 nm at an average accuracy score of 82.6 ± 2.1% by measured data sets of absorption and scattering signals. Furthermore, we demonstrated the concentration determination of plasmonic nanoparticle mixtures using a trained Support vector machine (SVM) classifier. Our simple yet sensitive nanofluidic detection platform will be a valuable tool for the analysis of nanoparticles and their applications to chemical and biological assays.

Analyzing radiowave multiple diffraction from a low transmitter in vegetated urban areas using a spherical-wave UTD–PO approach

This article introduces a uniform theory of diffraction–physical optics (UTD–PO) formulation for analyzing radiowave multiple diffraction emanating from trees and buildings in green urban areas, considering illumination from a low transmitter and assuming spherical-wave incidence. Based on Babinet’s principle, this solution models buildings as rectangular sections and accounts for the influence of tree crowns (assuming these rise above the average rooftop height) by incorporating appropriate attenuation factors/phasors into the diffraction phenomena of buildings. The validation of the formulation is achieved through measurements made at the 39 GHz 6G mmWave frequency on a scale model of a green urban environment comprising bonsai trees and bricks. The main advantage of the proposed solution is that the calculations only include single diffractions due to recursion, circumventing the need to use higher-order diffraction terms in the diffraction coefficients, thus reducing the computation time and power. Our results may be beneficial for the design of mobile communication systems, including 6G networks, situated in green urban areas and with transmission source positioned lower than the surrounding infrastructure.

Efficient Guided Wave Modelling for Tomographic Corrosion Mapping via One-Way Wavefield Extrapolation

Mapping corrosion depths along pipeline sections using guided-wave-based tomographic methods is a challenging task. Accurate defect sizing depends heavily on the precision of the forward model in guided wave tomography. This model is fitted to measured data using inversion techniques. This study evaluates the effectiveness of a recursive extrapolation scheme for tomography applications and full waveform inversion. It employs a table-driven approach, with precomputed extrapolation operators stored across a spectrum of wavenumbers. This enables fast modelling for extensive pipe sections, approaching the speed of ray tracing while accurately handling complex velocity models within the full frequency band. This ensures an accurate representation of diffraction phenomena. The study examines the assumptions underlying the extrapolation approach, namely, the negligible reflection and conversion of modes at defects. In our tomography approach, we intend to use multiple wave modes—A0, S0, and SH1—and helical paths. The acoustic extrapolation method is validated through numerical studies for different wave modes, solving the 3D elastodynamic wave equation. Comparison with an experimentally measured single-mode wavefield from an aluminium plate with an artificial defect reveals good agreement.

USE OF GPR TECHNOLOGIES IN THE ROAD CONSTRUCTION INDUSTRY

The article continues the study on determining the possibility of applying ground penetrating radar (GPR) technologies in the road construction industry. The authors conduct research using an antenna unit that registers the cross-polarisation component of the reflected signal. In this case, processing the obtained radar images comes down to subtracting two mutually orthogonal components of the signal, which allows the determination of areas of the environment with anisotropic properties. Identifying and positioning extraneous inclusions, finding communications, and determining the location of reinforcement in roadway and bridge structures are relevant tasks. Their solution lies in studying the phenomenon of wave diffraction on extraneous inclusions of the investigated environment. Metal inclusions of different diameters are distinctly visible on radar images obtained during laboratory research. The laboratory studies conducted by the authors showed that the shape and nature of the hyperbola of the diffracted wave significantly depend on the object’s depth, diameter, and material. Therefore, further research in this direction should aim at studying the shape of the diffracted wave, which ultimately allows for judging the depth of occurrence and the diameter of a local extraneous inclusion. When finding and identifying reinforcement in structural layers of road surfaces and elements of bridges, difficulties arise due to the spacing of the reinforcing mesh. With a small reinforcing mesh spacing, when the wavelength is longer than the spacing, the reflections from the adjacent reinforcement bars merge into a common continuous boundary and make the lower layers of the structure almost indistinguishable. Solving the mentioned difficulties is possible by improving the equipment base and the algorithms for processing and interpreting the received radar images. Completed theoretical studies and computational experiments allow us to state that the development of road surface thickness measurement and defect detection techniques will become the basis of the road surface monitoring system using the subsurface geolocation method. Keywords: ground penetrating radar, radar image, road surface, dielectric constant, defect detection, thickness measurement, local inclusions.

Gravity wave interaction with a heaving membrane above a thick porous bed

The present study analyzes diffraction and radiation phenomena of oblique waves interacting with a heaving floating membrane in the presence of a thick porous bed. Following the linear water wave theory, the physical problem is framed mathematically. The significance of the article resides in the following: (1) progressive wave analysis (water and membrane-covered region), (2) solving the boundary value problem (BVP) using the matched eigenfunction expansion method for diffraction and radiation problems, and (3) numerical illustration of various hydrodynamic coefficients for different membrane and porous bed parameters. Bragg scattering with varying frequency is observed for smaller values of membrane tension. Also, the present study demonstrates that the number of oscillations experienced by the reflection coefficient increases proportionally with the length of the membrane. Furthermore, cut-off membrane properties exist at a given frequency for which the zero minimum of wave force is obtained. Also, the porous bed's thickness impacts wave reflection and membrane deflection significantly. Thus, we found that the maximum reflection is observed for a fully permeable bed; however, it decreases with a decrease in the porosity of the porous medium because of its dissipative nature. Conversely, the added mass and damping coefficient increases with increased membrane length. The collective numerical observations for both diffraction and radiation provide insight into resonance phenomena, the role of membrane properties, and the intricate relationship between wave characteristics and membrane properties. The findings from this study could assist geologists and marine engineers in designing and managing ports and harbor infrastructure.

High precision detection of artificial defects in additively manufactured Ti6Al4V alloy via laser ultrasonic testing

Laser powder bed fusion (LPBF) is a cutting-edge metal additive manufacturing technology with promising applications in aerospace, biomedicine, and industrial automation. Its ability to fabricate intricate geometric shapes, achieve high surface precision, and deliver comprehensive results renders it highly advantageous. In LPBF process, several factors such as the interference of laser processing fluctuations, rapid cooling rate, and environmental gas, contribute to the initiation and expansion of defects including pores and cracks, limiting the application of LPBF components. Laser ultrasonic testing (LUT) is a promising non-destructive evaluation method that can accurately detected defects in LPBF manufactured components by non-contact generation and detection. In this paper, a multi-physical field LUT model for the pores and cracks in LPBF additively manufactured Ti6Al4V alloy is proposed. The interaction of ultrasound with defects produces defect reflection echo wave, diffracted wave, and transmission wave. The transmission and diffraction phenomena occur in the longitudinal sound waves at defects. Furthermore, the echo wave reflected at crack exhibited enhanced prominence and an irregular shape. Clear differences were observed in the effects of laser ultrasonic detection on different defect types, pore depths and sizes. Finally, the LUT technology achieved the detection of 90 μm pore defects in LPBF manufactured Ti6Al4V alloy.

De[formula omitted]Net: Under-display camera image restoration with feature deconvolution and kernel decomposition

While the under-display camera (UDC) system provides an effective solution for notch-free full-screen displays, it inevitably causes severe image quality degradation due to the diffraction phenomenon. Recent methods have achieved decent performance with deep neural networks, yet the characteristic of the point spread function (PSF) is less studied. In this paper, considering the large support and spatial inconsistency of PSF, we propose De2Net for UDC image restoration with feature deconvolution and kernel decomposition. In terms of feature deconvolution, we introduce Wiener deconvolution as a preliminary process, which alleviates feature entanglement caused by the large PSF support. Besides, the deconvolution kernel can be learned from training images, eliminating the tedious PSF-obtaining process. As for kernel decomposition, we observe regular patterns for PSFs at different positions. Thus, with a kernel prediction network (KPN) deployed for handling the spatial inconsistency problem, we improve it from two aspects, i.e., (i) decomposing the predicted kernels into a set of bases and weights, (ii) decomposing kernels into groups with different dilation rates. These modifications largely improve the receptive field under certain memory limits. Extensive experiments on three commonly used UDC datasets show that De2Net outperforms existing methods both quantitatively and qualitatively. Source code and pre-trained models are available at https://github.com/HyZhu39/De2Net.

Precision Modulation and the Shadow Blister Phenomenon in Optical Diffraction Using Straight-Edge Apertures

The shadow blister effect, depicting the distortion of shadows when two objects overlap, is an optical phenomenon observable in sunlight without requiring specialized lab equipment. Despite its seemingly straightforward nature, this effect challenges explanation through ray theory and the Fresnel diffraction equation in certain regions. Conversely, the shadow blister effect exhibits both linear and nonlinear behavior corresponding to the steady variation of the transverse distance between the two unplanar straight edges along the optical axis. This article explores the shadow blister effect alongside the diffraction of a straight edge, revealing fundamental aspects of the diffraction phenomenon. The experimental study introduces a diffraction model adept at elucidating the shadow blister effect. This model relies on an inhomogeneous fractal space, potentially generated by objects near their surfaces, including the edges of barriers.

Multi-scale terahertz image reconstruction

This paper proposes a novel terahertz (THz) image recovery algorithm and a new THz image dataset is publicly available. Because of transmission noise, artificial errors and problems with diffraction phenomena are among the main problems that cause degradation of THz images. The point spread function (PSF) in real transmission is first obtained using a terahertz imaging system. Experiments can generate degraded images and clean image datasets for supervised training of neural networks via terahertz PSF. A Depthwise Dense Instantiation Normalization Block (DwDIN Block) has been proposed to recover the datasets. We constructed a powerful multi-stage network (DwDINet) at each scale by utilizing the DwDIN module. For input and output, the results of each stage of the network and the original images are taken as input into the next layer in order to enhance the background information. DwDINet achieves state-of-the-art (SOTA) results on the two main THz datasets. To verify the generality of the model, we performed experiments on various image recovery tasks. According to the experimental results, the proposed model is of great potential for the field of low-level image clarification.

Canadian banknotes to explore the phenomenon of diffraction

Gratings and their well-known diffraction patterns are the basis of spectrometers to characterize light sources. Reciprocally, periodic peaks in the diffraction pattern of x-rays scattered by solids bring valuable information about the internal geometry of the crystal lattice, providing details about the arrangement of atoms in the solid. In both cases, periodic gratings are considered. What about non-periodic gratings? Is it possible to reconstruct any grating structure knowing its diffraction pattern? We answer this question by studying diffraction through the hologram hidden in a Canadian banknote. We measure the diffraction of near-infrared light to numerically reconstruct the grating structure using the Gerchberg–Saxton algorithm. We then compare this reconstructed grating structure with the picture of the grating structure observed with a phase-contrast microscope. Such an approach allows us to study diffraction from a perspective different from that usually taught at university.

Evaluation of beach response due to construction of submerged detached breakwater

Submerged detached breakwaters (SDBWs) have increasingly been used in recent times as an alternative against their emergent counterpart (EDBWs) to mitigate erosion because the former do not spoil the seascape. Both of these structures are (usually) constructed using precast concrete blocks or natural granite rocks, hence becoming permeable structures. For an EDBW, a parabolic bay shape equation can be readily used to estimate the planar shape of the shoreline behind the structure, but there is still no approach to estimate how the shoreline behind the SDBW is formed. In this study, we estimated how the shoreline is balanced by examining how the dominant wave direction changes due to the diffraction of the transmitted wave generated after the installation of the SDBW from the long-term wave directional spectrum. The change in dominant wave direction was determined under the shoreline gradient condition where littoral drift does not occur, considering the diffraction phenomenon due to the difference in transmitted waves. This means that the shape of the equilibrium shoreline changes to face perpendicular to the dominant wave direction. As a meaningful result, when the transmittance is 0, it converges to the well-known empirical equation of EDBW. The present methodology is validated by comparing the observed data (wave and shoreline change) from two beaches (Anmok and Bongpo-Cheonjin Beaches) on the eastern coast of Korea. This rational approach to shoreline changes behind permeable SDBWs will help in proactive review work for coastal management as well as beach erosion mitigation.

Spin‐Selective Trifunctional Metasurfaces for Deforming Versatile Nondiffractive Beams along the Optical Trajectory

AbstractExploring and taming the diffraction phenomena and divergence of light are foundational to enhancing comprehension of nature and developing photonic technologies. Despite the numerous types of nondiffraction beam generation technologies, the 3D deformation and intricate wavefront shaping of structures during propagation have yet to be studied through the lens of nanophotonic devices. Herein, the dynamic conversion of a circular Airy beam (CAB) to a Bessel beam with a single‐layer spin‐selective metasurface is demonstrated. This spatial transformation arises from the interplay of 1D local and 2D global phases, facilitating the 3D control of non‐diffractive light fields. An additional overall phase gradient and orbital angular momentum are introduced, which effectively altering the propagation direction and transverse fields of complex amplitude beams along the optical path. The manifested samples exhibit superior defect resistance, laying a crucial application in micro/nanolithography technologies. This approach expands the in‐plane spin‐selective mechanism and leverages the out‐of‐plane propagation dimension, allowing for integrated high‐resolution imaging, on‐chip optical micromanipulation, and micro/nanofabrication within a versatile nanophotonic platform.

Utilizing the phenomenon of diffraction for noise protection of roadside objects

Abstract Presented here is a constructive solution to the challenge of utilizing the diffraction phenomenon for mitigating noise around roadside objects caused by the movement of vehicles on transportation routes. In contrast to existing prototypes, the innovation of the proposed solution lies in the creation of an active system that concentrates and directs oscillations originating from transportation sources. This active system, centered around sound absorption and reflection, establishes protective barriers and focuses on sound vibrations. The incorporation of diffraction effects within the Fraunhofer zones, along with the utilization of Fresnel lenses, directs attention towards these vibrations. The technical objective of harnessing the diffraction phenomenon for noise reduction around roadside objects involves demonstrating the feasibility of using a Fresnel zone plate (FZP) tailored for a specific oscillation frequency. This plate should demonstrate the ability to effectively manipulate sounds of varying frequencies while retaining its diffractive focusing capabilities. The intrinsic frequency characteristics of diffractive elements cannot be eliminated due to the inherent nature of sound diffraction. Consequently, it is imperative to thoroughly investigate and account for these properties. A groundbreaking discovery has been made, confirming the phenomenon of noise concentration originating from transportation sources. This revelation suggests that when a FZP is employed at frequencies other than its designed frequency, the concentration of oscillations remains. However, only the focal point of concentration shifts. Through experimentation, it has been established that the same FZP can be employed for varying wavelengths within a range of approximately ±20% while adhering to diffraction conditions. The feasibility of employing the thin lens formula to focus oscillations following the passage through a FZP has been substantiated. This solution also delves into the principal focusing, frequency, and shaping characteristics of the diffractive elements within FZPs. Furthermore, a computed estimation of the acoustic field scattered by a diffraction grating is compared against experimental data. This validates the approach and its efficacy in practical scenarios. The potential of harnessing the diffraction phenomenon to concentrate and regulate noise from transportation sources, thereby safeguarding roadside objects, is presented as a promising avenue for exploration.

Voltage-controlled two-dimensional Fresnel diffraction pattern in quantum dot molecules

This study explores the influence of inter-dot tunneling effects within a quantum dot molecule on the Fresnel diffraction phenomenon. Our findings indicate that the Fresnel diffraction of the output probe Gaussian field can be manipulated by adjusting the inter-dot tunneling parameter’s strength and the characteristics of the coupling field. The inter-dot tunneling effect establishes a closed-loop system, setting conditions for the interference of the applied fields. We specifically examine a Laguerre–Gaussian (LG) coupling field, investigating how its properties-such as strength, value, and sign of the orbital angular momentum (OAM)-impact the Fresnel diffraction of the output probe field. Increasing the inter-dot tunneling parameter and the coupling LG field’s strength allows for control over the spatial distribution of the Fresnel diffraction pattern. Notably, the inter-dot tunneling parameter can disturb the symmetry of the diffraction patterns. Additionally, considering a negative OAM for the coupling LG field transforms the diffraction pattern into its inverse shape. This suggests that, in the presence of the inter-dot tunneling effect, the Fresnel diffraction pattern is contingent on the direction of rotation of the helical phase front of the coupling LG field. Our results offer insights into quantum control of Fresnel diffraction patterns and the identification of OAM in LG beams, presenting potential applications in quantum technologies.

Ultra-Thin and Broadband P-Band Metamaterial Absorber Based on Carbonyl Iron Powder Composites.

The field of P-band (0.3-1 GHz) absorption has witnessed rapid development in metamaterial absorbers due to their exceptional designability and the absence of restrictions imposed by the one-fourth wavelength rule. In this study, we combined carbonyl iron powder (CIP) composites with a periodic structure composed of metal capacitive patterns and employed a genetic algorithm (GA) to optimize the electromagnetic parameters of the CIP substrate. By selecting the appropriate shape and material for the units of pattern based on transmission line theory, as well as regulating relevant structural parameters, we successfully designed an ultra-thin broadband metamaterial absorber for the P-band. Experimental results demonstrate that within the range of 0.3-0.85 GHz, the reflection loss of our absorber remains below -5 dB, with a maximum value of -9.54 dB occurring at 0.45 GHz. Remarkably, this absorber possesses a thickness equivalent to only 1/293 of its working wavelength. Then, we conducted analyses on electric field distribution, magnetic field distribution, and energy loss density. Our findings suggest that high-performance absorption in metamaterials can be attributed to λ/4 resonant or coupling effects between structural units or diffraction phenomena. This absorber offers several advantages, including broad low-frequency absorption capability, ultra-thin profile, and convenient fabrication process, thus providing valuable theoretical insights for designing metamaterial structures.