Wave Plate Research Articles

A Periodic Extension to the Fokas Method for Acoustic Scattering by an Infinite Grating

The Fokas method (also known as the unified transform method) is used to investigate acoustic scattering by thin, infinite grating by extending the methodology to apply to spatially periodic domains. Infinite grating is used to model a perforated screen, a material of interest in aeroacoustics and noise reduction. Once the method is established, its numerical results are verified against the Wiener–Hopf (WH) technique, which has solved the problem only for a special case. A key benefit of the novel approach is that the scatterer, modelled as an infinitely repeating unit cell consisting of a thin, rigid plate, can take any length. This is in contrast to the WH method, where the plate length is restricted to half the width of the unit cell (for this method, no such restriction exists). The numerical method is an over-sampled collocation method of the integral equation resulting from applying the Fokas method: the global relation. The only increase in complexity in adapting the Fokas method to more complicated cell geometries is a higher number of terms in the global relation. The proportion of energy transmitted and reflected by the grating structure is assessed for varying incident wave angles, frequencies, and plate lengths.

Multi-Tap Optical Delay Line-Based Optical-Electrical Dispersion Compensation Scheme in High-Speed IM/DD Systems

Multi-Tap Optical Delay Line-Based Optical-Electrical Dispersion Compensation Scheme in High-Speed IM/DD Systems

Dispersion characteristics of Lamb wave in a multilayered magnetoelectroelastic plate with an imperfect interface

In this study, we investigate Lamb wave propagation in a multilayered magnetoelectroelastic plate with an imperfect magnetoelectroelastic interface using the generalized linear spring model (GLSM). The dispersion relation of the Lamb wave is obtained using an improved Legendre polynomial expansion method, which converts the wave problem into a linear eigenvalue system. The effectiveness of the present method was verified through comparison with two existing cases: SH wave in a bilayer plate with an imperfect interface and Lamb wave in a bilayer plate with a perfect interface. Numerical examples were presented for various multilayered plates composed of BaTiO3/CoFe2O4. The effects of the spring constant combinations, including the degree of mechanical, electric, and magnetic interface imperfections, layer thickness ratio, electromagnetic boundary condition, and stacking sequence on the dispersion characteristics are illustrated. The effect of the thickness ratio on the magneto-electromechanical coupling factor and the sensitivity of the phase velocity at different frequencies to changes in the interface characteristics are also discussed. The present investigation is of practical interest for developing new layered composite structures made of smart piezoelectric and piezomagnetic materials for engineering applications.

Resolving Artifacts and Improving the Detection Limit in Circular Differential Scattering Measurement of Chiral and Achiral Gold Nanorods.

Circular differential scattering (CDS) spectroscopy has been developed as a powerful method for the characterization of the optical activity of individual plasmonic nanostructures and their complexes with chiral molecules. However, standard measurement setups often result in artifacts that have long raised concerns on the interpretation of spectral data. In fact, the detection limit of CDS setups is constrained by the high level of artifacts, to ±10%. We address this issue by means of a detailed theoretical description of changes in the polarization state when circularly polarized light is reflected at a dark-field condenser. As a result, we propose a modified CDS configuration based on sequentially placing the quarter-wave plate and linear polarizer within the detection optical path, to analyze the circular polarization state of the light scattered by individual particles. Extensive analysis demonstrates a detection limit of ±1.5% for the modified configuration, which is significantly lower than that for the conventional setup. As a standard system for CDS measurements, both achiral and chiral gold nanorods (AuNRs) were characterized using both setups. With achiral AuNRs, linear dichroism (LD) artifacts in the conventional setup are found to originate from LD present in the excitation light and are only present if anisotropic excitation is produced as a result of the misalignment of the excitation light to the condenser. With chiral AuNRs, CDS spectra recorded with the conventional setup depend on the orientation of the chiral AuNRs with respect to the x-axis of the microscope and are reversed compared to those on the colloid and measured in the modified configuration. The results are in good agreement with theoretical simulations for both configurations.

Sensitivity of Lamb waves in viscoelastic polymer plates to surface contamination

Sensitivity of Lamb waves in viscoelastic polymer plates to surface contamination

Active invisible metamaterial of elastic waves with double targets in a thick plate

Wave invisibility has received increasing attention due to its great theoretical value and application to aerospace, military and other fields. In this work, the invisible flexural cloak for double hole targets in an elastic thick plate is proposed and proportional integral derivative (PID) active control is applied. Based on Mindlin thick plate theory and wave function expansion method, the wave equation for the thick plate is derived and scattering mode coefficients are obtained. The influences of structural and material parameters on dynamic stress concentration, scattering amplitude and scattering cross section (SCS) for double targets are investigated. With the consideration of specific hole targets, the cloaking configuration includes cloaks 1 and 2 and consists of periodically arranged piezoelectric (PZT) patches. Every PZT patch is attached to the active circuit with PID control function. The theoretical and experimental results illustrate that the cloak can achieve an invisible function for double targets within multiple frequency regions. On the other hand, the cloak can reduce the dynamic stress concentration, scattering amplitude and SCS of the thick plate. Different from the original structure without control, the effective frequency range of the PID active cloak can be widely extended.

Incremental Optical Encoder Error Modeling and Compensation for Accurate Speed Acquisition in Non-Stationary Conditions

Incremental Optical Encoder Error Modeling and Compensation for Accurate Speed Acquisition in Non-Stationary Conditions

Polarization Imaging Method for Detection of Lung Cancer Based on Symmetrical Single LCVR

ABSTRACTLung cancer ranks among the three most prevalent cancers worldwide. Polarization imaging technology can effectively distinguish between cancerous and normal tissues. The most commonly applied method for cancer detection is the dual‐rotating wave plate polarization imaging system (DWRPIS), which is cumbersome and prone to significant error due to 60 mechanical rotations. To address this, our experiment leveraged the stability of the Liquid Crystal Variable Retarder (LCVR) and, based on existing theoretical foundations for simplifying the use of LCVRs, designed a symmetric single‐LCVR polarization imaging system (SSLPIS) for the first time to detect lung cancer images. The SSLPIS is easy to operate, completing the entire acquisition process in just 150 s, with effective Mueller matrix imaging and an overall accuracy rate of over 90%, offering a faster and more precise detection method. This new approach provides an innovative pathway for the rapid detection of lung cancer.

Multi-angle and full-Stokes polarization multispectral images using quarter-wave plate and tunable filter

Polarization multispectral imaging has advanced significantly due to its robust information representation capability. Imaging application requires rigorous simulation evaluation and experimental validation using standardized datasets. However, the current full-Stokes polarization multispectral images (FSPMI) dataset, while providing simulation data, is limited by image drift and spectral bands. To overcome these limitations and supplement experimental data, this paper introduces the multi-angle and full-Stokes polarization multispectral images (MAFS-PMI) dataset. The imaging system utilizes a rotatable quarter-wave plate (QWP) and a fixed liquid crystal tunable filter (LCTF) to modulate polarization information. Meanwhile, the LCTF allows switching between multiple spectral bands. The acquired multi-angle polarization multispectral images facilitate the experimental validation of encoding strategies and reconstruction algorithms. Additionally, the derived full-Stokes polarization multispectral images enable the simulation evaluation of imaging methods. The MAFS-PMI dataset involves 73 fast axis angles (0° to 180°), four Stokes parameters, five polarization parameters, 35 spectral bands (520 nm to 690 nm), 400 × 400 pixels, and 12 distinct objects. This dataset offers a valuable resource for developing advanced imaging methods.

Physics-driven untrained neural network for vortex beam compensation in adaptive optics aided underwater wireless optical communications

Orbital angular momentum (OAM) multiplexing is emerging as a critical technique for achieving high data capacity in underwater wireless optical communications (UWOC). Nonetheless, wavefront distortions induced by underwater turbulence compromise the orthogonality of OAM modes. In this paper, we introduce a physics-driven untrained learning approach for adaptive optics that operates independently of extensive amplitude datasets. Without iterative processing and pre-trained datasets, the underwater turbulence characteristics can be retrieved accurately by only relying on a one-shot distorted probe beam and a priori known amplitude of the probe beam. By leveraging a single distorted diffraction pattern and a priori known amplitude of the probe beam, the characteristics of underwater turbulence can be accurately retrieved without iterative processing or pre-trained datasets. Furthermore, by implementing a hybrid input/output alternating projection algorithm with a square constraint area, the retrieved underwater turbulence phase screen beyond the [0, 2π] range aligns with the target pattern. This consistency indicates that the proposed wavefront recovery technology is validated across a broad range of turbulence strengths. As a demonstration of feasibility, numerical simulations, and optical experiments were conducted to validate the compensation of OAM beams. Furthermore, the theoretical bit error rate (BER) and channel capacity were inferred based on the purity of OAM modes and the level of crosstalk.

Rotation-induced plasmonic chiral quasi-bound states in the continuum

Nanoscale light manipulation using plasmonic metasurfaces has emerged as a frontier in photonic research, offering strongly enhanced light–matter interactions with potential applications in sensing, communications, and quantum optics. Here, we unveil the realization and control of chiral quasi-bound states in the continuum (quasi-BICs) by judiciously rotating one of the paired plasmonic bricks and thereby influencing structural asymmetry. By precisely controlling the rotation angle, we enable continuous modulation of the radiation loss in quasi-BICs and transition from a perfect half-wave plate to a good absorber for the left-handed circularly polarized light. This transformation leverages the intrinsic chirality with moderately high circular dichroism of ∼0.35 in both simulation and experimental observations, manifesting unprecedented control over the chiral light within sub-wavelength scales. Theoretical modeling and numerical simulations complement our experimental findings, offering deep insights into underlying mechanisms and the role of symmetry breaking in realizing chiral quasi-BICs. The observed phenomena open new pathways for developing ultra-compact chiral photonic devices with tailored optical properties, including highly sensitive chiral biosensors, circular dichroism spectroscopy, and chiral flat optical components for information processing.

The effect of a magnetic field on the generation of free radicals in the interaction of quaternary ammonium compounds with hydroperoxides

The magnetic effects (ME) of a moderate magnetic field (MF, 600 mT) on the rate of radical generation (Wi) in mixed micellar systems of quaternary ammonium compounds with hydroperoxides (QAC-ROOH), measured by the inhibitor method, and the effect of magnetic field on the rate of radical polymerization initiated by radicals, generated from the surface by QAC chemisorbed on a solid carrier upon interaction with hydroperoxide dissolved in the monomer are compared. It has been established that in micellar solutions MF reduces Wi, ME ≈ –0.45. In the case of radical polymerization of styrene containing cumyl hydroperoxide on the surface of mica plates with a chemisorbed monolayer of QAC (CTAB or ACh), the polymerization rate increases in MF.

Effects of surface roughness of a waveplate on the development of diffractive polarization speckle

A rough-surfaced retardation plate is a particular polarization-dependent phase modulation device, whose performance is affected by its surface roughness structures. In previous research [J. Opt. Soc. Am. A 32, 2346 (2015)JOAOD60740-323210.1364/JOSAA.32.002346], its decorrelation and depolarization effects have been investigated under an assumption of a rough surface model with large covariance of thickness fluctuations, giving a fully developed speckle field by transmission/reflection. This paper continues the analysis of the rough-surfaced retardation plate and then focuses on a smooth roughness model. When the thickness fluctuation is relatively small, partially developed speckle will be generated. The statistics of partially developed polarization speckle with non-uniform spatial distribution of polarization state will be discussed in the form of the matrix elements of the coherence–polarization matrix. The propagation of the partially developed speckle field will be traced within the framework of the complex-valued ABCD matrix theory under paraxial approximation to reveal the evolution of its degree change of coherence and polarization on propagation. This means that Gaussian apertures are included in the optical train of elements. The differences in statistical features from fully developed polarization speckle are emphasized.

The propagation of flexural waves in a metamaterial plate with tunable low-frequency band gap

The propagation of flexural waves in a metamaterial plate with tunable low-frequency band gap

Dynamic characteristics analysis and optimization of oil tank

The response of oil tanks under dynamic loads is the key to ensuring safety, and the analysis of stiffness and strength is very necessary. Modal analysis was carried out on the oil tank to obtain the natural frequencies and vibration modes. Under specific excitation frequencies, the stress responses of the dangerous points of the front head, the rear head, the cylinder, and the transverse wave plate were calculated respectively. Three filling rates of 30 %, 50 % and 70 % were respectively selected for the structural response study, and the structural deformation and stress responses of the storage tank structure under the impact of different volumes of liquid were obtained. According to the dynamic response analysis, the structure of the front head and transverse wave plate were strengthened. It can be known from the comparison of mechanical properties that the optimized structure can significantly improve the stiffness and strength, and effectively ensure the safety of the oil tank.

Converting Gaussian to line beams with high efficiency by flat liquid crystal optical elements

Line-shaped laser beams are desired for applications ranging from ultrafast laser processing to metrology. Here we demonstrate that line-shaped laser beams with diffraction-limited line widths can be generated from Gaussian beams with high efficiency by using flat liquid crystal optical elements. The liquid crystal optical elements are designed based on the Pancharatnam-Berry (PB) geometric phase acquired by light passing through a half waveplate and fabricated by using a high-resolution molecular orientation photopatterning technique. We show that these liquid crystal PB optical elements can achieve a diffraction efficiency over 99%, yielding no zero-order light leakage. We further demonstrate beam shaping devices for converting Gaussian beams into crosshair-shaped beams. The design and fabrication methods presented in this paper are general and can be extended to meet other complex beam shaping needs.

Self-balanced and self-phase-corrected electro-optic sampling in a birefringent crystal.

Mid-to-far-infrared (IR) spectral content is recorded using the novel self-balanced and self-phase-corrected electro-optical (EO) sampling arrangement. Self-balancing guarantees that the electric field emerging from the EO crystal yields a signal of zero via a Wollaston prism and balanced photodetector (i.e., without a wave plate following the EO crystal) in the absence of the electric field being sampled. Moreover, self-phase-correction ensures a nearly frequency-independent phase difference between the probe electric field pulse and the electric field pulse generated within the EO crystal via second-order nonlinear optical interactions. The self-balanced and self-phase corrected arrangement has the potential to yield enhancement of EO signals recorded using previously investigated birefringent crystals (implemented within traditional EO sampling geometries) and deliver optimum EO signal strengths when considering unexplored birefringent crystals.

Determination of fast axis and phase retardation of wave plates using polarization common-path vortex interferometry.

This Letter introduces a method for identifying the fast axis and phase retardation of wave plates by means of polarization common-path vortex interferometry. The technique utilizes a composite polarized vortex beam interacting with the wave plate under test. By analyzing the azimuth angle of the dark fringe in the interference pattern, the wave plate's characteristics are accurately extracted. The method involves rotating the wave plate to align its principal axes, followed by determining the fast-axis orientation and the phase retardation based on the direction of the dark fringe. The measurement theory is presented, and the feasibility of the technique is substantiated through experimental demonstration.

Development of a Wollaston phase grating polarized interferometer for simultaneous generation of interferograms

Wollaston phase-grating interferometer is introduced to measure of the optical phase across various samples. The system employs a Wollaston prism to create two angularly separated beams and with orthogonal linear polarizations. Working as a quasi-common-path interferometer, one of these beams serves as a reference while the other acts as the sample. Circular polarization states are induced in each beam using a quarter-wave plate. Both beams are directed onto a 4-f imaging system, within which a 2D phase grating is positioned at the Fourier plane. This 2D grating enables the superposition of the two beams, generating a polarized interferogram. The characteristics of the diffractive elements cause the grating to produce replicas of interference patterns, which are centered around the diffraction orders of the 2D phase grating itself. Due to the presence of interference patterns with inherent π phase shifts, this configuration reduces the number of polarizers needed to implement phase shifting methods. It is shown that by using two polarizers it is possible to generate four phase shifts. A polarizer oriented at 0° covers two of the replicas and another polarizer oriented at π/4 covers the remaining interferograms. This configuration introduces phase shifts of ξ1 = 0, ξ2 = π/2, ξ3 = π and ξ4 = 3π/2. Results obtained for static and dynamic samples are presented, as well as the corresponding statistics on the repeatability of the configuration.

Comparison of outcome of lambda plate versus double plate fixation in AO Type C fractures of distal humerus in adults.

Objective: To compare the outcome of lambda plate versus double plate fixation in AO Type C fractures of the distal humerus in adults regarding bone union, range of motion and MEP score. Study Design: Randomized Clinical Trial. Setting: Sheikh Zayed Hospital, Lahore. Period: 1-01-2020 to 31-12-2020. Methods: After fitting in the inclusion criteria, 50 patients were signed up, 25 in each group. In group A, patients underwent surgery by using a lambda plate. In group B, patients underwent surgery by using a double plate. All this procedure was done by a researcher under the supervision of a supervisor. On follow up on each visit, patients were re-evaluated for MEP score. If MEP scores>75, then excellent to the good outcome was noted. Meanwhile, range of motion and bone union on x-rays was also evaluated. Results: In this study, the average age of the patients was 37.46±11.34 years; 32(64%). patients were male, while 18(36%). patients were females. After the 6th month, the excellent to good MEP score was noted in 23 patients (92%) of the double plate group versus the excellent to good MEP was found in 24 patients (96%) of lambda plate group, p-value=>0.999. After the sixth month, in the double plate group, the delayed union was noted in two patients (8%) of double plate group while in one patient (4%) of lambda plate group, p-value=0.261. Conclusion: This study concluded that in the management of fractures of distal humerus in adults, both lambda plate and double plate fixation are equally effective.