Polarization Filter Research Articles

Design of Magnetic Fluid-Enhanced Optical Fiber Polarization Filter

In this paper, we demonstrated a method of filling the air holes of a photonic crystal fiber (PCF), coated with gold film, with magnetic fluid (MF) to enhance the Surface Plasmon Resonance (SPR). The simulation results show that at the wavelength of 1260–1675 nm, the minimum loss coefficient of the y-polarization mode is 4.7 times that before filling with MF, and the x-polarization mode is 0.45 times greater. Then, based on this method, we designed a polarizing filter with a core diameter of 9 µm. The numerical simulation results indicate that it not only maintains the same core diameter as the single-mode fiber, but also has a larger bandwidth and a higher extinction ratio (ER). Additionally, we can optimize its ER at a specific wavelength by adjusting the magnetic field.

Dawn and dusk satellite quantum key distribution using time and phase based encoding and polarization filtering

Dawn and dusk satellite quantum key distribution using time and phase based encoding and polarization filtering

Ultra-wideband and high-efficiency polarization rotator based on liquid crystals

We propose a novel design of an asymmetrically anchored negative liquid crystal (LC) cell capable of linearly rotating the polarization axis of broadband light, with the rotation angle controlled by voltage. Unlike conventional LC cells that require polarization filters or retarders, our LC cell can directly modulate the polarization state of light without any additional components. The LC cell exhibits high polarization rotation efficiency over a wide wavelength range (200 nm to 2000nm), superior to the existing polarization modulators. We validate our design through theoretical calculations and numerical simulations, proving that a degree of linear polarization of over 0.95 can be achieved in the UV, visible, and NIR regions. Our design can be applied in optical communications, biological imaging, and spectroscopic technologies.

Characteristics study of a dual-wavelength polarization filter based on gold-filled square lattice photonic crystal fiber

This study proposes a polarization filter based on gold-filled photonic crystal fiber (PCF) with a square lattice structure. Utilizing the finite element method (FEM), the filtering characteristics of the model were numerically simulated. The dispersion relation and loss characteristics of this structure were analyzed, and the optimal structural parameters were obtained through structural adjustments. Furthermore, the performance of the filter was evaluated under a 2% variation in manufacturing tolerances for gold film thickness (), air hole spacing (), and air hole diameters () and (). Results indicated that at the 1310 nm and 1550 nm communication windows, the confinement losses of the filter were 1354.6 dB/cm and 869.04 dB/cm, respectively, while the losses for the -polarization were merely 16.97 dB/cm and 0.98 dB/cm. When the filter length was set to 0.5 mm, the maximum extinction ratios (ERs) for the two windows reached 588.2 dB and 370.6 dB, and the filter bandwidth extended to 640 nm. Moreover, the characteristics of the filter under manufacturing tolerances were computed, revealing that the filter’s performance remained stable and feasible despite manufacturing errors. The proposed rectangular gold-coated PCF is anticipated to have broad applications in optical fiber communication and optical information processing.

Unveiling the Role of Electronic, Vibrational, and Optical Features of the 1T' WSe2 Monolayer.

Understanding the optoelectronic profile and chemical stability of transition-metal dichalcogenides (TMDs) is crucial for advancing two-dimensional (2D) material applications, particularly in electronics, optoelectronics, and energy devices. Here, we investigate the structural, electronic, optical, and excitonic properties of the 1T' WSe2 monolayer. Phonon dispersion analysis confirmed the thermodynamic stability of this system. The 1T' WSe2 monolayer exhibits a small electronic band gap of 0.17 eV, and its linear optical response suggests the potential use as a polarizing filter due to its strong reflectivity at ŷ light polarization. Unlike the 1T' MoS2 system, 1T' WSe2 does not show an excitonic insulator phase. Instead, its exciton binding energy of 150 meV is consistent with values expected for 2D materials. This distinction underscores the unique electronic and optical properties of 1T' WSe2, positioning it as a promising candidate for advanced technological applications such as flexible electronics, photodetectors, and quantum computing. By exploring these properties, we can unlock the full potential of TMDs in creating innovative high-performance devices.

Twisted hyperbolic van der Waals crystals for chip-scale full Stokes mid-infrared polarization detection

Abstract Investigating the polarization properties of light in the mid-infrared (mid-IR) spectrum is crucial for molecular sensing, biomedical diagnostics, and IR imaging system technologies. Traditional methods, limited by bulky size and complicated fabrication process, utilize large rotating optics for full Stokes polarization detection, impeding miniaturization and accuracy. Naturally occurring hyperbolic van der Waals (vdW) material based devices can address these challenges due to their lithography-free fabrication, ease of integration with chip-scale platforms and room-temperature operation. This study designs a chip-integrated polarimeter by performing multi-objective optimization for efficient exploration of the design parameter space. The spatial division measurement scheme used incorporates six precisely designed linear and circular polarization filters, achieving high extinction ratios exceeding 30 dB and transmittance surpassing 50%, with fabrication tolerance of film thickness up to 100 nm. The proposed device represents a significant advancement in polarimetric detection, providing a compact, cost-effective solution and opens new avenues for on-chip mid-IR polarimetric detection in next-generation ultra-compact optical systems.

Poldw: A Python code to denoise 3C seismic data with a new threshold-free polarization technique

We present a Python code that implements a novel threshold-free polarization strategy for removing random noise from 3C linearly polarized seismic data. The code, which we refer to as polarization denoising through windowing (poldw), uses closed-form formulas along sliding windows that span the data to determine the optimal rotation angles that allow the transfer of most of the signal energy to a given component. The denoised 3C data are obtained after canceling out the other two components, which are assumed to contain predominantly noise, and then rotating back. The method is simple and efficient because it only requires setting the sliding window length. Synthetic and microseismic field data examples show the method’s effectiveness, which significantly improves the signal-to-noise ratio without the need for threshold-based polarization filters. Therefore, these filters can be pipelined in the rotation-based strategy for additional noise removal if necessary. When the data set contains nonlinearly polarized data or significant nonrandom noise, the method is likely to fail. For robustness against non-Gaussian noise and outliers, poldw allows for the use of alternative norms similar to the [Formula: see text]- or [Formula: see text]-norms instead of the energy. In addition to the code, we provide a Jupyter notebook to illustrate the method step by step and reproduce the results of the field data example.

Optical Methods for Optimizing Fluorescence Imaging Field of View and Image Quality in Surgical Guidance Procedures.

Cancer surgery is aimed at complete tumor resection and accurate lymph node detection. However, numerous blood vessels are distributed within the tumor, and the colors of the tumor, blood vessels, and lymph nodes are similar, making observations with the naked eye difficult. Therefore, tumors, blood vessels, and lymph nodes can be monitored via color classification using an operating microscope to induce fluorescence emission. However, as the beam width of the LED required to induce fluorescence emission is narrow and the power loss of the beam is significant at a certain working distance, there are limitations to inducing fluorescence emission, and light reflection occurs in the observation image, obstructing the view of the observation area. Therefore, the removal of reflected light is essential to avoid missing the diagnosis of the lesion under observation. This paper proposes the use of a beam mirror and polarizing filter to increase the beam width and beam intensity. The refraction and reflection effects of the beam were utilized using the beam mirror, and the rotation angle of the polarizing filter was adjusted to remove light reflection. Consequently, the minimum beam power using the beam mirror was 10.9 mW, the beam width was doubled to 40.2°, and more than 98% of light reflection was removed at 90° and 270°. With light reflection effectively eliminated, clear observation of lesions is possible. This method is expected to be used effectively in surgical, procedural, and diagnostic departments.

Management of white spot enamel lesions with resin infiltration: potentials and future research directions.

The current study1 is a randomized controlled trial with two arm, multicenter and parallel group design. Study subjects were 38 orthodontic patients younger than 17 years who were being treated with metal braces. Patients with at least one white spot lesion (WSL) graded 1 to 2 according to the International Caries Detection and Assessment System (ICDAS) on the labial surface of permanent maxillary and mandibular canines and incisors were included for the trial. Teeth with carious lesions and restorations, anomalies of the enamel, and primary teeth were excluded. Patients were allocated by computer generated random sequence into resin infiltration and fluoride varnish intervention groups. Study subjects were blinded until the allocation, outcome assessors and statisticians remained blinded through the study, however the operators could not be blinded. Resin infiltration treatment involved removal of orthodontic wires and auxiliaries followed by cleaning the teeth with fluoride free prophylactic paste and completing the resin infiltration according to manufacturer's instructions. In the fluoride varnish group, a thin layer of the material was applied after isolating the teeth, and patients were asked not to eat or drink for 1 hour. This was continued twice a month for 6 months. Digital images of the teeth were obtained before, and 1 day (T1), 1 week (T2), 1 month (T3), 3 months (T4) and 6 months (T5) after treatment, using a DSLR camera and a matching polarization filter. The images were processed for calibration and color stability. Regions of interest representing WSL (white spot lesion) and SAE (sound adjacent enamel) were isolated in the images for comparison at different stages the images were captured. Statistical analysis was performed using SPSS version 28. Independent-samples t-test was utilized for comparison between the two groups, and paired-samples t-test for comparison within the groups. A statistical significance level of α = 0.05 was set. At T1, significant color difference was observed between white spot lesion and adjacent sound enamel in the resin infiltration group and it remained stable after 6 months. Whereas in the fluoride varnish group, there were no statistical differences from baseline to 6 months. A statistical difference of 3.27 CIELAB units (p < 0.001) was reported between the infiltration group and the fluoride group at T5. No significant changes were noted in SAE with respect to changes in lightness. Resin infiltration was found to be better at masking the demineralization produced by WSL and also enhanced the esthetic appearance of demineralized areas around the brackets. Resin infiltration did not produce any clinically visible effects in non-affected enamel. These changes remained stable for a period of 6 months.

Microelectromechanical System-Based Reconfigurable Terahertz Metamaterial for Polarization Filter, Switch, and Logic Modulator Applications.

The terahertz (THz) metamaterials integrated with microelectromechanical systems (MEMS) have led to the realization of dynamic control in amplitude, phase, polarization, and spin angular momentum of the THz wave. In this study, we demonstrate an MEMS-based reconfigurable THz metamaterial (RTM) composed of a split ring resonator (SRR) for real-time modulation of THz wave. By gradually increasing the polarization angle of the incident THz wave, the resonant frequency of SRR switches from 0.74 to 1.16 THz, and the maximum modulation depth is more than 70%. When the MEMS-based RTM is actuated by different DC bias voltages, the polarization-dependent transmission intensity and resonant frequency of the device can be actively tuned. MEMS-based RTM shows logical function characteristics that can be used for logic modulators by performing the driving voltages and polarization states as 2-bit input signals and quantizing the transmission response as "on" and "off" states. The logic gates of "NAND" are at 0.439 THz and "AND" is at 0.732 THz. These results offer potential applications for the proposed MEMS-based RTM in tunable and reconfigurable polarization filters, optical switches, programmable logic modulators, and so on.

Dual-window polarization filtering characteristics of rectangular photonic crystal fibers

This paper presents a photonic crystal fiber (PCF) polarization filter with a square array arrangement of gold film fillings, allowing for filtering at dual wavelengths. The paper analyzes the dispersion characteristics and loss properties of this structure and optimizes the structural parameters through adjustments to achieve the best performance. At 1310 nm, the confinement losses of x and y polarization fundamental modes are 903.54 dB/cm and 30.51 dB/cm, respectively; at 1640 nm, the confinement losses of y and x polarization fundamental modes are 479.02 dB/cm and 88.72 dB/cm, respectively. The corresponding filtering bandwidths are 390 and 350 nm, while the full width half maximum (FWHM) is 59.56 nm, indicating excellent selectivity and resolution of the filter. The performance metrics, such as confinement loss, extinction ratios, and bandwidth, are compared in the paper with those reported for other filters. Additionally, the study also analyzed the filter’s performance under varying manufacturing tolerances of gold film thickness and air hole diameter by 5%, revealing that the filter’s performance remains stable and feasible even in the presence of errors.

Polarization-filterless polarization-sensitive polarization-multiplexed phase-shifting self-reference digital holography

I propose a phase-shifting self-reference digital holography technique in which both three-dimensional (3D) and polarization information is simultaneously obtained without any polarization filters. A Fourier-transform lens, a polarization beam splitter, and two phase-only spatial light modulators are used to simultaneously generate self-reference holograms with orthogonal polarization directions. 3D and polarization information is multiplexed in the recorded phase-shifted digital holograms and retrieved by applying polarization-selective phase-shifting interferometry and numerical refocusing. The validity of the proposed technique is experimentally demonstrated.

Spin Polarization via Adiabatic and Counterdiabatic Engineering.

A spin filter is a device that allows only a single spin state to pass, equivalent to a polarizing filter for a beam of light. Here, taking inspiration from shortcuts to adiabaticity, I demonstrate that the potential landscape of a typical quantum point contact can be tuned to act as a two terminal spin filter or to generate a spin-polarized beam. The effect presented is sufficiently robust that rough engineering yields a significant effect, as demonstrated by experiments on asymmetrically biased quantum point contacts in InAs quantum wells.

Polarization analysis and filtering of undersampled 3C seismic data in the frequency-slowness domain

Polarization filters have emerged as a useful tool for coherent noise denoising in multicomponent seismic data. By exploiting the polarization properties of seismic waves, these filters can significantly improve wave-type separation, which is a crucial step in seismic data processing. However, their effectiveness in land seismic data in complex areas can be impacted by the presence of scattering noise, and their applicability is limited by irregular spatial sampling, which hinders velocity information for wave-type discrimination. To address these limitations, we introduce a novel two-step method for distinguishing and separating polarized wave types in shot gathers captured from a spatially undersampled linear array of 3C vector sensors. The first step involves conducting a polarization analysis in the frequency-slowness domain using elliptical elements derived from the linear Radon transform of the seismic data. The second step isolates specific polarized waves using the 3C frequency-slowness polarization filter (3C-FSPF), a technique that uses tailored taper functions based on polarization analysis. Our method stands out from single-station filters that cannot use velocity information for wave-type discrimination and existing multistation filters that require regularly sampled data. To evaluate our method, comprehensive tests are conducted on synthetic and real data. The results consistently demonstrate the effectiveness of 3C-FSPF in separating diverse polarized wave types under conditions of irregular and sparse spatial sampling and noise. Our findings underscore the potential of this method for advancing exploration geophysics by enhancing the quality of seismic data, particularly in land regions with complex near-surface structures.

Numerical analysis of an all-fiber plasmonic polarization filter using dual elliptical gold thin layers deposited photonic crystal fiber

In order to solve the problems of high performance and small size incompatibility, as well as limited bandwidth, of traditional polarization filters in optical communication systems, this work presents an all-fiber polarization filter using dual elliptical gold layer deposited photonic crystal fiber by the finite element tool. The gold layers are plated on the inside of the two elliptical holes to create surface plasmon resonance effect, which cause the signal intensity in x-polarized direction to be much greater than that in y-polarized direction. The simulation results illustrate that when hole-to-hole pitch Λ is 2.0 μm, cladding hole diameter d 1 is 2.0 μm, two inner-holes’ diameter d 2 is 0.3 μm, spacing between two inner-holes d s is 0.755 μm, the major axis length of elliptical holes a is 2.0 μm, the minor axis length of elliptical holes b is 0.97 μm, the gold thin layer t is 100 nm, the proposed PCF filter exhibits good filtering performance at the communication wavelength of 1.55 μm, where the confinement loss in x- and y-polarized direction are 303.91 dB cm−1 and 0.06 dB cm−1, respectively. The crosstalk and operating bandwidth improve with the increment of device’s length, the 800 μm-long PCF filter possesses the maximum crosstalk of −211.14 dB and the bandwidth of 600 nm. Finally, the experimental scheme is also discussed. We believe that this photonic filter can play a significant role in optical communication, optical sensing, spectral analysis, and other related fields.

Numerical simulation of an in-fiber broadband plasmonic polarization filter using photonic crystal fiber with dual elliptical gold layers

The demand for advanced and compact photonic filters is increasing in today's optical communication systems. This work introduces a new all-fiber broadband polarization filter using photonic crystal fiber with dual elliptical gold layers. The filtering performance is evaluated and analyzed by the finite element method. The simulation results demonstrate that the two elliptical gold layers can effectively induce a significant change in the energy of x-polarized light, leading to a great difference between the two polarized lights. By selecting reasonable structural parameters of the proposed PCF, the 1 mm-long in-fiber filter has a maximum extinction ratio of -108.90 dB, a low insertion loss of 0.64 dB around 1.31 µm and an ultra-broad bandwidth of 1020 nm, covering two common communication windows of 1.31 µm and 1.55 µm. Additionally, the filtering experimental scheme is discussed. This filter is expected to drive the advancement of optical integrated chips and all-optical communication networks.

Polarization filter of hollow-core anti-resonant fiber in the 1550 nm band based on SPR effect

Hollow-core anti-resonant fiber (HC-ARF) with unique light propagation through air present a promising avenue for advanced applications of polarization filters based on HC-ARF. This paper proposes a single-mode and single-polarization filters (SMSPF) around 1550 nm based on HC-ARF with tellurite glass as the substrate material. The polarization filtering characteristics of the HC-ARF with varying wall thickness and gold wire filling are simulated and analyzed using the finite element method. A single-mode single-polarization (SMSP) HC-ARF with a continuous bandwidth of 30 nm is obtained, and a polarization filter with low polarization loss and a high filtering bandwidth of 390 nm is achieved through the surface plasmon resonance (SPR) effect.

Tunable chalcogenide solid-core anti-resonant fiber polarization filter based on SPR effect

Based on surface plasmon resonance (SPR), we proposed a tunable chalcogenide solid-core anti-resonant fiber (SC-ARF) polarization filter. The purpose of introducing the SPR, which is excited by coating the inner wall of the cladding tubes with a gold film, is to achieve a discrepancy between the confinement loss of two polarized fundamental modes (FMs). The full-vector finite element method (FV-FEM) evaluates the impact of fiber core radius, cladding tube radius, cladding tube wall thickness, and gold film thickness on the polarization filter characteristics. The results show that when the thickness of the gold film is 30 nm and the fiber length is 4 mm, the filter bandwidth can simultaneously cover the S + C + L optical communication band and reach 248 nm, and the extinction ratio (ER) value reaches -377.46 dB. Moreover, we also confirmed the tuning effect of the gold-coated cladding tube wall thickness on the resonance wavelength. The proposed fiber polarization filter has potential application value in optical fiber communication and transmission.

Filter-free lens-free polarimetric incoherent digital holography

I propose an incoherent digital holography (IDH) technique in which four-dimensional (4D, three-dimensional (3D) coordinates and polarization) information is simultaneously obtained using neither polarization filters nor lenses. A filter-free lens-free self-interference incoherent interferometer for 4D imaging is designed and developed. Four-dimensional (4D) information is multiplexed in recorded phase-shifted incoherent holograms and extracted by polarization-selective phase-shifting interferometry. The validity of the proposed holography for multiplexed 4D imaging is experimentally demonstrated by the constructed filter-free lens-free self-interference IDH system and a randomly polarized light-emitting diode.

POLarizer-FENestration (POLFEN) a novel concept of a glazing technology to modulate daylighting and glare in buildings

A conceptual new window/glazing technology called POLarizer-FENestration (POLFEN) is presented. In 1935, Edwin Land's pioneering work on polarizers successfully developed a sheet polarizer that was used in various applications. Subsequently, polarizers were employed in windows to modulate daylight and reduce associated glare. Early prototype windows were circular in shape so that the polarizing filter could be rotated to modulate the daylight. However, compared to rectangular-shaped windows that are ubiquitous, circular windows are rare in buildings. Therefore, a new window/glazing technology, discussed in this paper, was developed that utilizes a polarizing film in a conventional rectangular or square window, arranged in the form of strips or a checker-grid over the window panes to modulate daylighting levels and control glare. In this new research, a working prototype of the glazing technology is developed and demonstrated including simulations using the Radiance daylighting simulation software. In the current work, two types of measurements were taken: photographs of the indoor luminous environment and illumination levels (Lux) at selective points on the work-plane both in a physical prototype as well as in the simulation model under two sky conditions: CIE clear sky with sun, and overcast sky. The results indicate that the new glazing technology resulting from this concept can effectively modulate daylighting levels, minimized associated glare to an acceptable level while maintaining a view to the outdoor environment. The technology can be classified as Variable Transmission Glazing (VTG), similar to Electrochromic (EC) glazing since it also offers a dynamic modulation of solar optical properties (Tvis).