Polarization Filter Research Articles

High-loss and broadband photonic crystal fiber polarization filter with two large apertures coated with gold layers

A high-loss broadband photonic crystal fiber polarization filter based on surface plasmon resonance is designed. The designed filter has two symmetrical large holes, and the holes are coated with a metal film, which greatly improves the loss. The characteristics of the polarization filter are calculated by the finite element method. The thickness of the metal layer and the arrangement and size of air holes near the core are discussed. The optimum structure of a metal-filled polarization filter in photonic crystal fibers is obtained. By modulating the parameters, the loss of the filter in the $y$y direction at 1.31 µm is 3261.7 dB/cm, while the loss in the $x$x direction is small. If the length of the optical fiber is set to 200 µm, the extinction ratio is greater than 20 dB, and the width is 1 µm, respectively. The filter has a simple structure and excellent performance.

Two alternative process routes for recovering pure indium from waste liquid crystal display panels

Abstract Recovering indium from liquid crystal display (LCD) screen waste is important from a sustainability point of view for several reasons: the environmentally hazardous metals are not landfilled, the recovery process involves lower CO2 emissions than primary production, and supply from secondary sources matches the continuously increasing demand of indium. In this study, two alternative process routes for recycling the critical metal, indium, from LCD panel waste were studied and compared using laboratory and bench-scale experiments. The first process was a conventional hydrometallurgical process that involves manual dismantling, hammer mill crushing of the glass, cross-current sulfuric acid leaching of the metals, and liquid-liquid extraction separation of indium. Using this process, over 99% pure indium solution can be produced with a recovery yield of over 70%. The second process is novel because it includes (manual) scraping of the indium tin oxide (ITO) layer from the glass panels, followed by sulfuric acid leaching of the metals. The yield of indium was over 80%, and the purity of the resulting solution was over 99%. The solutions obtained from either of the suggested processes were sufficiently pure for cementing indium in high purity. The novel process appears much more straightforward and economically more feasible because the polarizing filter need not be removed and the liquid-liquid extraction purification step is excluded. Moreover, less amount of leaching acid is required.

A polar filter in DNA polymerases prevents ribonucleotide incorporation.

The presence of ribonucleotides in DNA can lead to genomic instability and cellular lethality. To prevent adventitious rNTP incorporation, the majority of the DNA polymerases (dPols) possess a steric filter. The dPol named MsDpo4 (Mycobacterium smegmatis) naturally lacks this steric filter and hence is capable of rNTP addition. The introduction of the steric filter in MsDpo4 did not result in complete abrogation of the ability of this enzyme to incorporate ribonucleotides. In comparison, DNA polymerase IV (PolIV) from Escherichia coli exhibited stringent selection for deoxyribonucleotides. A comparison of MsDpo4 and PolIV led to the discovery of an additional polar filter responsible for sugar selectivity. Thr43 represents the filter in PolIV and this residue forms interactions with the incoming nucleotide to draw it closer to the enzyme surface. As a result, the 2’-OH in rNTPs will clash with the enzyme surface, and therefore ribonucleotides cannot be accommodated in the active site in a conformation compatible with productive catalysis. The substitution of the equivalent residue in MsDpo4–Cys47, with Thr led to a drastic reduction in the ability of the mycobacterial enzyme to incorporate rNTPs. Overall, our studies evince that the polar filter serves to prevent ribonucleotide incorporation by dPols.

A broadband single mode single polarization metal wires-embedded hollow core anti-resonant fiber for polarization filter

Abstract A broadband single mode single polarization metal wires-embedded hollow core anti-resonant fiber for polarization filter is designed and investigated by the finite element method in this paper. When there are no metal wires, the hollow core anti-resonant fiber has a broadband single mode property by adjusting structure parameters. Then, through embedding two symmetrical metal wires into fiber, only one polarized state of fundamental mode suffers a high loss due to the selective excitation of surface plasmon resonance. The effects of three kinds of metal wires (gold, silver and aluminum) on the hollow core anti-resonant fiber are investigated in detail. Simulation results demonstrate that the hollow core anti-resonant fiber with aluminum wires has the best single polarization characteristics. Its polarization and high order mode extinction ratios are greater than 100 within a broad wavelength range from 1.26 to 1.58 μm. The low loss of the polarized fundamental mode is 0.33 dB/m and 0.99 dB/m at the wavelength of 1.31 μm and 1.55 μm, respectively. The proposed broadband single mode single polarization fiber has a potential application as a polarization filter in coherent optical systems, interferometric fiber sensors and fiber gyroscopes.

Fine Structure and Spin Dynamics of Linearly Polarized Indirect Excitons in Two-Dimensional CdSe/CdTe Colloidal Heterostructures

Heterostructured two-dimensional colloidal nanoplatelets are a class of material that has attracted great interest for optoelectronic applications due to their high photoluminescence yield, atomically tunable thickness, and ultralow lasing thresholds. Of particular interest are laterally heterostructured core-crown nanoplatelets with a type-II band alignment, where the in-plane spatial separation of carriers leads to indirect (or charge transfer) excitons with long lifetimes and bright, highly Stokes shifted emission. Despite this, little is known about the nature of the lowest energy exciton states responsible for emission in these materials. Here, using polarization-controlled, steady-state, and time-resolved photoluminescence measurements, at temperatures down to 1.6 K and magnetic fields up to 30 T, we study the exciton fine structure and spin dynamics of archetypal type-II CdSe/CdTe core-crown nanoplatelets. Complemented by theoretical modeling and zero-field quantum beat measurements, we find the bright-exciton fine structure consists of two linearly polarized states with a fine structure splitting ∼50 μeV and an indirect exciton Landé g-factor of 0.7. In addition, we show the exciton spin lifetime to be in the microsecond range with an unusual B-3 magnetic field dependence. The discovery of linearly polarized exciton states and emission highlights the potential for use of such materials in display and imaging applications without polarization filters. Furthermore, the small exciton fine structure splitting and a long spin lifetime are fundamental advantages when envisaging CdSe/CdTe nanoplatelets as elementary bricks for the next generation of quantum devices, particularly given their ease of fabrication.

Ultra-Broadband Hyperuniform Disordered Silicon Photonic Polarizers

We present the first experimental demonstration at the optical telecommunication band of near-isotropic and transverse-electric (TE) photonic bandgap (PBG) in a hyperuniform disordered photonic structured (HUDPS) wall network. Next, we propose and demonstrate state-of-the-art performance of a hyperuniform disordered silicon photonic (HUDSiP) polarizer. The TE mode is blocked by the combined effects of reflection due to a wide PBG in the optimal wall network structure, scattering, and radiative bandedge resonances. The transverse-magnetic (TM) mode is allowed to pass through with a small insertion loss (IL). A 12.9-μm-long HUDSiP polarizer is experimentally demonstrated with an ultrabroad bandwidth of 240 nm (1440-1680 nm) when the extinction ratio (ER) ≥ 30 dB and IL ≤ 3 dB for the TM mode. The measured spectrally averaged ER and IL of the TM mode are 41.4 dB and 0.8 dB (0.4 dB at 1550 nm), respectively. A 38.7-μm-long HUDSiP polarizer shows an average IL for the TE mode of 54.9 dB and ER of 53.0 dB. Tests of 40-Gbps on-off-keying data transmission through the HUDSiP polarizers show clear eye diagrams. The HUDSiP polarizers are promising in polarization filtering in the large-scale polarization-sensitive/diverse silicon photonic circuits for high-speed optical interconnects.

Meiotic spindle avoidance using a polarizing filter at the time of ICSI, a step closer towards individualized ICSI

To assess the impact of routine meiotic spindle identification during intra-cytoplasmic sperm injection (SI-ICSI), on fertilization and blastocyst formation rates when compared against conventional intra-cytoplasmic sperm injection (ICSI). All ICSI cycles undertaken between February 2015 and December 2016 in two similarly run IVF centers were included. At February 2016, spindle identification was introduced into routine practice. ICSI was performed following standard protocols: polar body was positioned either at 6 or 12 o’clock and used as reference for sperm injection at 3 o’clock. SI-ICSI oocyte identification was performed just before ICSI under 40 times magnification and then rotated until polar body was positioned at 12 o’clock. At this point a polarizer filter (Olympus IX2), was inserted while light turned to maximum intensity. Oocytes were rotated until a birefringent spindle was identified. Spindle position and intensity was recorded by embryologist as 0/+/++/+++, with 0 being assigned to spindle absence and +++ to maximum spindle intensity when compared against the most birefringent area in zona pellucida. Sperm injection was performed at 3 o’clock. Fertilization and blastocyst formation rates were recorded blind to spindle characteristics. Comparison was performed using Fisher’s Exact test. With an increased 5% normal fertilization rate and 7% higher blastocyst rate, this study suggests that visualizing the oocyte meiotic spindle using an inexpensive polarizing filter at the time of ICSI can avoid inadvertent damage and leads to improved normal fertilization and blastocyst formation. Other potential benefits could include better timing for injection in accordance with cytoplasmic maturation. Prospective studies would be needed to validate this later concept.

Three-Dimensional Microscopic Surgical Videos: A Novel and Low-cost System

Three-dimensional (3D) imaging and videos are a very useful tool in the neurosurgical training, although unfortunately the 3D systems available have a very high cost. The objective of this study is to describe a novel and low-cost 3D microsurgical video system. To obtain the 3D videos we use a surgical microscope, 2 video adapters, 2 cameras, and an HDMI cable. A video editor program is used for processing the videos. For the projection we use a computer with PowerPoint (Microsoft, Inc, Redmond, WA) software, a video splitter, DVI cables, 2 projectors, 2 polarization filters, and a "silver screen" with polarized glasses. By using 2 equal cameras and video adaptors in each beam splitter port it was possible for us to obtain 2 videos that were equivalent to the images received by both surgeon's eyes. Using the video signal of both cameras during processing resulted in a 3D stereoscopic recording with Final Cut (Apple, Inc, Cupertino, CA) software. The polarized 3D format provided the best projection conditions. It does not alter the original colors of the videos and its prolonged visualization was more comfortable. The main advantage of this method is the ability to show in a realistic way the spatial relationships and the depth of the structures captured with the microscope. This paper presents in a clear and detailed way how to create and use a low-cost 3D surgical video system.

Lateral Leakage in Silicon Photonics: Theory, Applications, and Future Directions

This paper presents an overview of lateral leakage in silicon photonics due to polarization coupling between the guided mode of a ridge waveguide and unguided slab mode in the etched cladding. We explain the physical origins and provide insight into how this effect can be suppressed or harnessed. We show how lateral leakage can manifest as new resonant behaviour and explore this effect in the context of bound states in the continuum. We review a number of applications for devices based on lateral leakage and present outlook for a new generation of polarization manipulators, antennas and filters.

Nature-inspired chiral metasurfaces for circular polarization detection and full-Stokes polarimetric measurements

The manipulation and characterization of light polarization states are essential for many applications in quantum communication and computing, spectroscopy, bioinspired navigation, and imaging. Chiral metamaterials and metasurfaces facilitate ultracompact devices for circularly polarized light generation, manipulation, and detection. Herein, we report bioinspired chiral metasurfaces with both strong chiral optical effects and low insertion loss. We experimentally demonstrated submicron-thick circularly polarized light filters with peak extinction ratios up to 35 and maximum transmission efficiencies close to 80% at near-infrared wavelengths (the best operational wavelengths can be engineered in the range of 1.3–1.6 µm). We also monolithically integrated the microscale circular polarization filters with linear polarization filters to perform full-Stokes polarimetric measurements of light with arbitrary polarization states. With the advantages of easy on-chip integration, ultracompact footprints, scalability, and broad wavelength coverage, our designs hold great promise for facilitating chip-integrated polarimeters and polarimetric imaging systems for quantum-based optical computing and information processing, circular dichroism spectroscopy, biomedical diagnosis, and remote sensing applications.

3D INSPECTION OF THE RESTORATION AND CONSERVATION OF STAINED GLASS WINDOWS USING HIGH RESOLUTION STRUCTURED LIGHT SCANNING

Abstract. The initial focus of this research was on the development of a general workflow for the documentation and monitoring of historical stained glass windows using structured light scanning. Therefore windows from different churches, time periods and with different corrosion and damage phenomena were scanned before and after conservation measures. To evaluate the execution of the restoration measures the data was compared using 3D inspection software to examine the differences in geometry between the two scans. Various problems had to be solved, for example, how to deal with heavily reflective surfaces and the extreme contrast between light and dark surfaces, as seen in the borders between ‘Schwarzlot’ painting and plain glass. The application of materials for matting the surfaces, such as Cyclododecane spray, was impossible due to the high accuracy of the surface measurement required for 3D inspection. Regarding the contrast differences of the surfaces, the creation of exposure fusions and the use of polarization filters to reduce reflections were tested. In addition to the general problems encountered when recording translucent surfaces, the historical glasses caused additional problems in calculating surface comparisons. For example, the windows have to be moved and turned around several times, both during the conservation process and while scanning, causing deformations of the geometry due to the flexible lead rods allowing a certain degree of movement.

Enlightening force chains: a review of photoelasticimetry in granular matter

A photoelastic material will reveal its internal stresses when observed through polarizing filters. This eye-catching property has enlightened our understanding of granular materials for over half a century, whether in the service of art, education, or scientific research. In this review article in honor of Robert Behringer, we highlight both his pioneering use of the method in physics research, and its reach into the public sphere through museum exhibits and outreach programs. We aim to provide clear protocols for artists, exhibit-designers, educators, and scientists to use in their own endeavors. It is our hope that this will build awareness about the ubiquitous presence of granular matter in our lives, enlighten its puzzling behavior, and promote conversations about its importance in environmental and industrial contexts. To aid in this endeavor, this paper also serves as a front door to a detailed wiki containing open, community-curated guidance on putting these methods into practice.

Chip-integrated plasmonic flat optics for mid-infrared full-Stokes polarization detection

Flat optics presents a new path to control the phase, amplitude, and polarization state of light with ultracompact devices. Here we demonstrate chip-integrated metasurface devices for polarization detection of mid-infrared light with arbitrary polarization states. Six high-performance microscale linear and circular polarization filters based on vertically stacked plasmonic metasurfaces (with total thickness <600 nm) are integrated on the same chip to obtain all four Stokes parameters of light with high accuracy. The device designs can be tailored to operate at any wavelength in the mid-infrared spectral region and are feasible for on-chip integration with mid-infrared (mid-IR) photodetectors and imager arrays. Our work will enable on-chip mid-IR polarimeters and polarimetric imaging systems, which are highly desirable for many applications, such as clinical diagnosis, target detection, and space exploration.

Cholesterol Crystals Induce Coagulation Activation through Complement-Dependent Expression of Monocytic Tissue Factor.

Cholesterol crystals (CC) are strong activators of complement and could potentially be involved in thromboinflammation through complement-coagulation cross-talk. To explore the coagulation-inducing potential of CC, we performed studies in lepirudin-based human whole blood and plasma models. In addition, immunohistological examinations of brain thrombi and vulnerable plaque material from patients with advanced carotid atherosclerosis were performed using polarization filter reflected light microscopy to identify CC. In whole blood, CC exposure induced a time- and concentration-dependent generation of prothrombin fragment 1+2 (PTF1.2), tissue factor (TF) mRNA synthesis, and monocyte TF expression. Blocking Abs against TF abolished CC-mediated coagulation, thus indicating involvement of the TF-dependent pathway. Blockade of FXII by corn trypsin inhibitor had a significant inhibitory effect on CC-induced PTF1.2 in platelet-free plasma, although the overall activation potential was low. CC exposure did not induce platelet aggregation, TF microparticle induction, or TF on granulocytes or eosinophils. Inhibition of complement C3 by CP40 (compstatin), C5 by eculizumab, or C5aR1 by PMX53 blocked CC-induced PTF1.2 by 90% and reduced TF+ monocytes from 18-20 to 1-2%. The physiologic relevance was supported by birefringent CC structures adjacent to monocytes (CD14), TF, and activated complement iC3b and C5b-9 in a human brain thrombus. Furthermore, monocyte influx and TF induction in close proximity to CC-rich regions with activated complement were found in a vulnerable plaque. In conclusion, CC could be active, releasable contributors to thrombosis by inducing monocyte TF secondary to complement C5aR1 signaling.

Stereoscopic imaging capsule endoscopy in a single lens design based on prisms and polarizers

This paper proposes a capsule endoscopy (CE) with stereoscopic imaging that is based on a single lens design. There is a prism array installed in front of the single lens to merge two separate fields of views (FOVs) into the field of the lens. Such a merging field involves two view information. A scheme applies a pair of orthogonal polarizations coated on the outside faces of individual prisms for multiplexing these two different views. The rays from the two fields go through the single lens to form the separate images by applying polarization filter with interleaving arrangement (that is, space division process) of the states in front of the image sensor. Another way is to apply a liquid crystal array (LCA) with active polarization function in time division process to receive the separate images. We employ the optical software, Zemax, to simulate and analyze the proposed CE. The simulation results show that the proposed CE can successfully receive the two field images in the image plane by using only a single lens.

Towards optimal single-photon sources from polarized microcavities

An optimal single-photon source should deterministically deliver one and only one photon at a time, with no trade-off between the source's efficiency and the photon indistinguishability. However, all reported solid-state sources of indistinguishable single photons had to rely on polarization filtering which reduced the efficiency by 50%, which fundamentally limited the scaling of photonic quantum technologies. Here, we overcome this final long-standing challenge by coherently driving quantum dots deterministically coupled to polarization-selective Purcell microcavities--two examples are narrowband, elliptical micropillars and broadband, elliptical Bragg gratings. A polarization-orthogonal excitation-collection scheme is designed to minimize the polarization-filtering loss under resonant excitation. We demonstrate a polarized single-photon efficiency of 0.60+/-0.02 (0.56+/-0.02), a single-photon purity of 0.975+/-0.005 (0.991+/-0.003), and an indistinguishability of 0.975+/-0.006 (0.951+/-0.005) for the micropillar (Bragg grating) device. Our work provides promising solutions for truly optimal single-photon sources combining near-unity indistinguishability and near-unity system efficiency simultaneously.

Individual selective rotation of the linear polarization of single light beam in a bundle.

An approach for aligning of linear polarized light beams with different wavelengths into a single beam with parallel linear polarization is presented and experimentally demonstrated. The main idea is based on the application of recently developed composite half-wave plates, working as linear polarization filters.

Propagating sentiment signals for estimating reputation polarity

The emergence of social media and the huge amount of opinions that are posted everyday have influenced online reputation management. Reputation experts need to filter and control what is posted online and, more importantly, determine if an online post is going to have positive or negative implications towards the entity of interest. This task is challenging, considering that there are posts that have implications on an entity's reputation but do not express any sentiment. In this paper, we propose two approaches for propagating sentiment signals to estimate reputation polarity of tweets. The first approach is based on sentiment lexicons augmentation, whereas the second is based on direct propagation of sentiment signals to tweets that discuss the same topic. In addition, we present a polar fact filter that is able to differentiate between reputation-bearing and reputation-neutral tweets. Our experiments indicate that weakly supervised annotation of reputation polarity is feasible and that sentiment signals can be propagated to effectively estimate the reputation polarity of tweets. Finally, we show that learning PMI values from the training data is the most effective approach for reputation polarity analysis.

A V-shape photonic crystal fiber polarization filter based on surface plasmon resonance effect

In this paper, a V-shape photonic crystal fiber (PCF) polarization filter based on surface plasmon resonance (SPR) effect is proposed. With the full vector finite element method, the V-shape photonic crystal fiber polarization filter is designed, and the coupling characteristics between the core mode and surface plasmon polariton mode are analyzed. The simulation results show that the fiber parameters have significant effects on the shift and strength of the SPR wavelength. Moreover, the losses of the core modes along the Y and X polarization directions are 68904 dB/m and 858 dB/m at the SPR wavelength of 1550 nm, respectively. Finally, the extinction ratio and error-tolerant rate of extinction ratio are also analyzed. The proposed V-shape PCF polarization filter can achieve good filtering effect in the communication band and is easy to integrate with existing optical fiber communication and sensing systems.

Fast copolymer network liquid crystals for tunable birefringence colors.

A fast-switching, tunable color filter was found in a copolymer network liquid crystal (LC), which was in situ generated in a conventional LC test cell with parallel aligned glass plates and investigated with polarized light. Polarization filters were used to convert the tunable optical phase retardance of the test cells to birefringence colors as is always possible in a LC test cell with carefully adjusted cell gap and effective birefringence. The cell gap of the samples could be adjusted to a value of 9 μm, which is not easily possible in a polymer LC composite without creating defects. In these samples, the typical pastel colors seen frequently in birefringent samples could be avoided. The transmittance spectra were recorded and converted to CIE 1931 color coordinates, which showed that the colors seen had a reasonable distance to the white point. The electro-optic switching times of the samples were investigated: Fast responses of t on +t off <5 ms were found, which is an impressive speed for tunable birefringence colors in LCs and LC composites. Upon increasing addressing voltages, a blueshift of the peak seen in the transmittance spectra was observed. The samples consisted of copolymer network LC, generated from a reactive mixture with mesogenic monomer and nonmesogenic comonomer. The tunable color was seen selectively in samples with dodecyl acrylate as comonomer. The experiments show how even a straightforward electro-optic experiment still can result in unexpended findings, which may expand the use of LC composites in nondisplay applications. The polymer morphology in samples with a larger cell gap was investigated with scanning electron microscopy, and interdefect distances of ≈40 μm were found. The appearance of defects in test cells with a cell gap of 9 μm could be avoided because the cell gap was much smaller than the measured interdefect distances in test cells with a larger cell gap.