Wave Plate Research Articles

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.

Enhancing high-order harmonic mode-locking in Er/Yb-Doped fiber lasers with sub-MHz fundamental frequency via optoacoustic resonance

We present an experimental study of a long Er/Yb-doped fiber ring laser with a low fundamental frequency of 0.678 MHz. By solely adjusting the quarter-wave plate in the polarization controller, we uncovered a series of reproducible laser generation regimes. Among these, multiple soliton bunches were harmonically mode-locked to low-order cavity harmonics (from the 3rd to the 8th). Notably, we also identified a regime featuring a stable soliton train harmonically mode-locked to the 472nd cavity harmonic at 320 MHz. This regime demonstrated exceptional harmonic mode-locking stability, with a supermode suppression level of 49 dB corresponding to the timing jitter on the order of a few picoseconds. We attribute this remarkable stability to an exact optoacoustic resonance between the laser repetition rate and the fiber eigen acoustic mode frequencies, specifically identified as R06 and TR2,15. These findings represent a significant advancement in high-performance fiber laser operation, particularly in enhancing the stability of lasers with sub-MHz fundamental frequencies capable to generate regular pulses with much higher repetition rates.

Effects of surface roughness of a wave plate on the development of diffractive polarization speckle

Effects of surface roughness of a wave plate on the development of diffractive polarization speckle

Light control using a double-stacked liquid crystal cell with enhanced viewing angle–blocking performance

In the future, there will be technological challenges between providing entertainment to passengers and eliminating driver distractions to ensure safety. Viewing angle control technologies for automotive display panels depending on each mode are required to integrate and provide both entertainment and advanced driver assistance system functions because watching videos while driving is regulated in most countries. In automotive display panels, unique electro-optical characteristics are required to control blocking or transmission only from the driver's direction while always being well observed from the passenger's direction. In this study, we developed a viewing angle control technology using double-stacked twisted nematic liquid crystal (TN-LC) films with excellent light-blocking performance only in the driver's direction over wide polar angle ranges in the privacy mode. By configuring the two TN-LC films in ordinary-ray mode and the other in the extraordinary-ray mode, the light could be completely blocked in the privacy mode, whereas it remained well transmitted in the normal mode in a specific left direction. Moreover, using double-stacked TN-LC films, light leakage at high polar angles in the privacy mode can be completely eliminated even without an optical compensation film, which is typically used to eliminate light leakage at high polar angles. Electro-optical films based on polarization optics are potential candidates for accelerating the growth of infotainment in self-driving cars.

Precision compensation method for large-scale measurements based on full-space refractive index field reconstruction with vibratory mirror background oriented schlieren (VMBOS)

With the development of the large-scale equipment manufacturing industry, such as aircraft component assembly, wind turbine rotor blade measurement and large ship assembly the demand for optical measurement accuracy in large-dimensional spaces within industrial environments has become increasingly stringent. However, due to the presence of internal interference sources, light will no longer propagate in a straight line, thereby introducing measurement errors that cannot be ignored. To compensate for the measurement error, the refractive index field distribution within the large-dimensional measurement space must be reconstructed. Therefore, this paper proposed a vibratory mirror background oriented schlieren (VMBOS) based on vibratory scanning. This method scans the measurement space through the rotation of vibratory mirror to obtain light deflection angles at different directions. Subsequently, the refractive index field of the large-dimensional space is reconstructed by using the tomographic reconstruction algorithm. Then the optical path of the light in the optical measurement can be corrected through the Hamiltonian ray tracing algorithm, thereby achieving compensation for the measurement error. Finally, the VMBOS method has been verified through both simulation and experimental methods. The experimental results demonstrated that the method proposed in this paper can be applied to optical path correction and error compensation in large scale spaces.

Impact of the continuity of spinning rate function on circular SOP conversion performance in spun quarter wave plate

Spun quarter wave plate (SQWP) exhibits superior state of polarization (SOP) conversion performance compared to the conventional quarter wave plate (QWP), with low loss and high accuracy, making it a promising choice for fiber optic systems. The spinning rate function, as a crucial component of SQWP, characterizes the process of spinning rate (ξ) from 0 to maximum (ξmax), playing a vital role in the performance of SQWP. To enhance circular SOP conversion, the traditional way is that we raise the spinning rate, but this increases ellipticity fluctuation (ΔE), impacting SQWP stability. Urgent exploration of alternative solutions is needed. In order to address this issue, in this study, the impact of the continuity of spinning rate function on circular SOP conversion performance in SQWP is thoroughly investigated through theoretical research and numerical simulation. The results show that spinning rate functions with higher order continuity decrease ellipticity fluctuation and enhance the circular SOP conversion performance in SQWP more effectively. We introduce and compare two novel higher order continuous spinning rate functions with the conventional linear and cosine functions regarding their robustness (σ) on circular SOP conversion performance. The average values of σ for the two proposed spinning rate functions are 4.01×10−5 and 2.17×10−6, respectively. They are one and two orders of magnitude smaller than the linear and cosine functions. The results demonstrate that the proposed spinning rate functions outperform conventional linear and cosine functions in both circular SOP conversion performance and robustness. The research findings of this study are expected to offer valuable insights and guidance for the future development and design of SQWP.

Peculiarities of Lamb Waves Propagating in Functionally Graded Layers

Propagation of harmonic Lamb waves in plates made of functionally graded materials (FGM) with transverse inhomogeneity is studied by the modified Cauchy six-dimensional formalism. For arbitrary transverse inhomogeneity a closed form dispersion equation is derived. Dispersion relations for materials with different kinds of inhomogeneity are obtained and compared.

A Mura model‐based optical compensation for organic light‐emitting diode display luminance nonuniformity utilizing two image capturing

AbstractIn this paper, we proposed a new optical Mura compensation method that requires only a few Mura detections for all gray levels. We analyzed the characteristics of Mura resulting from process variations in the thin film transistor (TFT) of each pixel and developed a new model using a logarithmic function. The proposed compensation algorithm has been verified with simulation and experimental results. We found that the uniformity of the proposed compensation algorithm at 7G, 24G, 75G, 100G, 150G, and 255G, which required only two image captures, was comparable to those that required five captures. The model improved uniformity from 41.32% to 68.60% at 0.18 nit brightness, demonstrating its effectiveness. Additionally, the method significantly reduces the number of image captures needed from five to two and decreases the image capturing process time from 2183 to 150 ms, saving over 14 times in process efficiency. The proposed methodology demonstrates significant advancements in achieving luminance uniformity in OLED displays, addressing mass production constraints.

Low-noise 2-GHz figure-9 fiber laser based on passive harmonic mode-locking.

We have proposed and demonstrated the generation of a high-repetition-rate ultrashort pulse with long-term stability and low noise based on a harmonic mode-locked (HML) figure-9 fiber laser. Different HML orders from the 2nd to the 13th are generated by adjusting the pump power, net dispersion, and wave plate angles. A 2-GHz HML pulse is obtained with a 155-MHz fundamental repetition rate in a Yb-doped fiber laser, and the corresponding supermode suppression level is as high as 50 dB. The average power of the output pulse is nearly 200 mW, and the compressed pulse duration is 535 fs. To the best of our knowledge, 2 GHz and 196 mW represent, respectively, the highest repetition rate and output power in a figure-9 fiber laser. This work offers a potential pathway to achieve high-repetition-rate ultrashort pulses in the GHz range with high power and low noise levels.

Polarization-insensitive optical coherence tomography using pseudo-depolarized reference light for mitigating birefringence-related image artifacts.

Optical coherence tomography (OCT) images are prone to image artifacts due to the birefringence of the sample or the optical system when a polarized light source is used for imaging. These artifacts can lead to degraded image quality and diagnostic information. We aim to mitigate these birefringence-related artifacts in OCT images by adding a depolarizer module in the reference arm of the interferometer. We investigated different configurations of liquid crystal patterned retarders as pseudo-depolarizers in the reference arm of OCT setups. We identified the most effective depolarization module layout for polarization artifact suppression for a spectral-domain OCT system based on a Michelson and a Mach-Zehnder interferometer. The performance of our approach was demonstrated in an achromatic quarter-wave plate allowing the selection of a variety of sample polarization states. A substantial improvement of the OCT signal magnitude was observed after placing the optimal depolarizer configuration, reducing the cross-polarization artifact from 5.7 to 1.8dB and from 8.0 to 1.0dB below the co-polarized signal for the fiber-based Michelson and Mach-Zehnder setup, respectively. An imaging experiment in the birefringent scleral tissue of a post-mortem alpine marmot eye and a mouse tail specimen further showcased a significant improvement in the detected signal intensity and an enhanced OCT image quality followed by a drastic elimination of the birefringence-related artifacts. Our study presents a simple yet cost-effective technique to mitigate birefringence-related artifacts in OCT imaging. This method can be readily implemented in existing OCT technology and improve the effectiveness of various OCT imaging applications in biomedicine.

Ultrahigh-reflectivity chiral mirrors based on the metasurface of the quarter-waveplate

A study is conducted on a GaAs-based high-contrast subwavelength chiral metasurface (HCCM) designed for 1064 nm. The metasurface integrates a high-contrast subwavelength grating (HCG) for TM mode modulation, a SiO2 support layer, and a compact quarter-waveplate (QWP) to convert linearly polarized light to circularly polarized light. The HCG achieves ultra-high reflectivity at 1064 nm, attributed to the large refractive index contrast between the Si grating and SiO2 layer. The designed HCCM has a reflectivity of more than 99 % for the TM mode and less than 80 % for the TE waves in the wavelength range of 1050 nm–1085nm, and it can also excite the circularly polarized light with an absolute error of less than 0.03 at the transmitting end in the case of the 1064 nm TM wavelength. These results suggest that circular dichroic metasurfaces could offer a promising approach for photonic manipulation in circular polarization VCSELs, potentially reducing the manufacturing challenges and costs associated with traditional methods.

Anti-ballistic properties of hybrid UHMWPE fiber-reinforced composite armour

The ballistic performance of three hybrid composite plates, including ultra-high molecular weight polyethylene (UHMWPE), UHMWPE/Aramid, and UHMWPE/CFRP with similar surface density, was studied in the paper. These plates were tested under the impact of 7.62×25 mm full metal jacket (FMJ) bullets, with the dynamic back deformation (BFD) captured using Digital Image Correlation (DIC) technology. The effects of material combinations and striking faces on the dynamic response were discussed. The deformation and penetration mechanisms were analyzed using optical microscopy and micro-CT tomography. The results indicated that the UHMWPE/CFRP plate exhibited the lowest BFD, followed by UHMWPE and the UHMWPE/Aramid plate. When UHMWPE severed as the striking face, the fibers underwent through-thickness compression, which transitioned to in-plane tension and led to an elongated fracture of yarns. Similarly, Aramid fibers also experienced tensile fractures under similar conditions. In contrast, carbon fibers had brittle shear fractures when CFRP was the striking face. Additionally, the “V-shaped” cone traveling hinge velocity was calculated using DIC results, and the effects of the plate bending stiffness and wave impedance on protective performance were discussed. The findings emphasize the importance of an optimal material configuration to mitigate the propagation of compressive waves in the thickness direction and enhance bending stiffness, which is crucial for improving protection within ballistic limits.

Controllable temporal twisting polarization within an ultrafast laser pulse.

We propose a method for controlling the time-varying polarization of optical pulses by introducing a quarter-wave plate into a 4-f pulse shaper and using a spatial light modulator to impose a group delay. This setup enables the polarization state of the incident pulse to vary over time. Specifically, for linearly chirped incident pulses, the polarization ellipse twists uniformly over time, while its ellipticity changes monotonically. As the group delay increases, the pulse intensity gradually splits in the time domain, transitioning from a single pulse with uniformly twisting polarization to two circularly polarized pulses with opposite chirality. We provide a detailed and comprehensive explanation of this modulation process using analytical expressions.

Non-Hermitian Sensing in the Absence of Exceptional Points.

Open systems possess unique potentials in high-precision sensing, yet the majority of previous studies rely on the spectral singularities known as "exceptional points." Here, we theoretically propose and experimentally demonstrate universal non-Hermitian sensing in the absence of exceptional points. The scheme makes use of the intrinsic sensitivity of a non-Hermitian probe to weak external fields, which can be understood as the direct consequence of non-Hermiticity. We confirm the basic mechanism by simulating the sensor-field dynamics using photon interferometry, and, as a concrete example, demonstrate the enhanced sensing of signals encoded in the setting angle of a wave plate. While the sensitivity of the probe is ultimately limited by the measurement noise, we find the non-Hermitian sensor showing superior performance under background noises that cannot be suppressed through repetitive measurements. Our experiment opens the avenue of enhanced sensing without exceptional points, complementing existing efforts aimed at harnessing the unique features of open systems.

Low-frequency propagating and evanescent waves in strongly inhomogeneous sandwich plates

The paper aims at studying dispersion of elastic waves in a sandwich plate with the parameters, characteristic of aerogel core and hard skin layers, typical for aerospace applications including optimal design of fuselage structural components. The proposed approach relies on multiparametric analysis, taking into account the effect of strong transverse inhomogeneity. It is demonstrated that both an additional low-frequency propagating wave and a slowly decaying evanescent one appear due to a high contrast in geometric and mechanical parameters of the layers. The key findings include the derivation of two-mode asymptotic expansions of the full dispersion relation at the low-frequency limit, as well as elucidation of the non-trivial link between long-wave evanescent and propagating modes. A sophisticated composite nature of the obtained expansions involving various shortened forms is investigated. The range of validity for each of these forms over frequency and wave-number domains is evaluated. Comparison of asymptotic results with the numerical solution of the full dispersion relation is presented.

Topological interface and corner states of flexural waves in metamaterial plates with glide-symmetric holes

This study investigates the topological localization and propagation of flexural waves in metamaterial plates with perforated holes exhibiting glide symmetry. The dispersion relations of flexural waves in this mechanical system exhibit four-fold Dirac degeneracies at the M point of the Brillouin zone. By properly adjusting the rotation angles of the perforated holes, these degeneracies can be lifted up to create omnidirectional bandgaps, enabling nontrivial topological phases. Both numerical and experimental results demonstrate multiple topological states of flexural waves in the developed elastic metaplates, including dual-band helical interface states and anisotropic interface/corner states. The simple perforated metaplates with glide-symmetric holes provide novel, manufacturable platforms for the flexible manipulation of topological flexural waves, greatly facilitating potential applications such as energy harvesting and signal enhancement.

Modeling and Analysis of Ellipticity Dispersion Characteristics of Lamb Waves in Pre-stressed Plates

Modeling and Analysis of Ellipticity Dispersion Characteristics of Lamb Waves in Pre-stressed Plates

Optimal multi-spectrum polarization detection with full-Stokes in a single channel by using standard retarders

Polarization detection with full-Stokes is one of the important way to obtain spatial distribution and physical information on targets. However, the most full-Stokes multi-spectrum polarization detection system is relatively complex, as the traditional method is generally designed for multi-channel to adapt the different wavelength. In this paper, we propose an optimal polarization detection method to obtain the full-Stokes vector of the incident light in one channel for different wavelengths. This method utilizes two standard retarders for multi-spectrum full polarization modulation, which can obtain accurately the desired retardance to achieve optimal system performance at multi-wavelengths. The numeric analysis validates the feasibility of the dual-retarders detection system based on tunable polarization retardance method. Furthermore, in experiments, just two much more readily available quarter-wave plate (QWP) retarders are utilized, the various special retardance within 0.2° errors and high polarization measurement accuracy below 10-2 level at multi-wavelengths are achieved. This method, with a simple structure, has excellent application prospects in high-precision polarization detection, such as solar magnetic field detection.

Multichannel vortex beam array based on quarter-wave plate metasurface

Multichannel vortex beam array based on quarter-wave plate metasurface