Dichroic Polarizers Research Articles

Deployment of POLARBEAR-2b

POLARBEAR-2b (PB-2b) is the second receiver in the Simons Array, a cosmic microwave background (CMB) polarization experiment. The Simons Array uses dichroic polarization sensitive lenslet-coupled sinuous antennas and transition-edge sensor (TES) bolometers made of superconducting films. These bolometers are read out with frequency multiplexing electronics. PB-2b contains ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document} 7500 detectors in two bands at 90 and 150 GHz with arcminute resolution. The polarization of these detectors is modulated by a cryogenic continuously rotating half-wave plate. PB-2b was installed on its telescope in 2022 in the Atacama Desert at an altitude of 5.2 km. This paper will detail initial readout commissioning, test of a new loopgain monitoring method, and focusing the optics. Work is ongoing to commission the remaining ambient temperature readout electronics, measure detector time constants, and observe with the cryogenic half-wave plate spinning

Exploring the dust grain size and polarization mechanism in the hot and massive Class 0 disk IRAS 16293-2422 B

Context. Multiwavelength dust continuum and polarization observations arising from self-scattering have been used to investigate grain sizes in young disks. However, the likelihood of self-scattering being the polarization mechanism in embedded disks decreases for very highly optically thick disks and makes us reconsider some of the size constraints from polarization, particularly for younger and more massive disks. The 1.3 mm polarized emission detected toward the hot (≳400 K) Class 0 disk IRAS 16293-2422 B has been attributed to self-scattering, with predictions of bare grain sizes between 200 and 2000 µm. Aims. We aim to investigate the effects of changing the maximum grain sizes in the resultant continuum and continuum polarization fractions from self-scattering for a hot and massive Class 0 disk extracted from numerical simulations of prestellar core collapse and to compare them with IRAS 16293 B observations. Methods. We compared new and archival dust continuum and polarization observations at high resolution between 1.3 and 18 mm to a set of synthetic models. We developed a new publicly available tool to automate this process called Synthesizer. This tool is an easy-to-use program for generating synthetic observations from numerical simulations. Results. Optical depths are in the range of 130 to 2 from 1.3 to 18 mm, respectively. Predictions of significant grain growth populations, including amax = 1000 µm, are comparable to the observations from IRAS 16293 B at all observed wavelengths. The polarization fraction produced by self-scattering reaches a maximum of approximately 0.1% at 1.3 mm for a maximum grain size of 100 µm, which is an order of magnitude lower than the grain size observed toward IRAS 16293 B. Conclusions. From comparison of the Stokes I fluxes, we conclude that significant grain growth could be present in the young Class 0 disk IRAS 16293 B, particularly in the inner hot region (< 10 au, T > 300 K) where refractory organics evaporate. The polarization produced by self-scattering in our model is not high enough to explain the observations at 1.3 and 7 mm, and such effects as dichroic extinction and polarization reversal of elongated aligned grains remain other possible but untested scenarios.

Synthesis and Properties of Room-Temperature Phosphorescent Liquid Crystal Copolymers with Linearly Polarized Luminescence Characteristic.

Room-temperature phosphorescent (RTP) liquid crystal materials have garnered considerable attention because of their significant applications in organic light emitting diodes, polarized light emitting materials, and so forth. How to efficiently synthesize pure organic RTP liquid crystals and regulate their performance is of great significance. In this article, we propose a simple and feasible method to synthesize RTP liquid crystals and manipulate their properties through copolymerization. We constructed RTP liquid crystal copolymers by copolymerizing a phosphorescent monomer bearing biphenyl mesogen with a phosphorescent monomer bearing a dibenzofuran chromophore. All the synthesized copolymers show a liquid crystal property because of the introduction of biphenyl mesogen. Meanwhile, by changing the composition of copolymers, it is possible to regulate their RTP performance, including luminescence color and lifetime. As the content of the PMDFM0C component in copolymers increases, the phosphorescence lifetime gradually increases. For poly(MDFM0C(0.46)-co-MBi18C(0.54)), the phosphorescence lifetime can reach 463.0 ms. Moreover, the phosphorescence color of the PMDFM0C component in copolymers changes with the copolymer composition, which can induce variable room-temperature phosphorescence. In addition, when oriented, liquid crystal copolymer films can emit linearly polarized fluorescence and linearly polarized phosphorescence. The linearly polarized phosphorescence dichroic ratio and polarization ratio values of the oriented poly(MDFM0C(0.46)-co-MBi18C(0.54)) film are 3.33 and 0.50, respectively.

Complex Fourier demodulation approach for the dual rotation polarizer-analyzer polarimeter

In this research, we propose a demodulation algorithm for the dual rotation polarizer-analyzer polarimeter. The proposal retrieves the partial Mueller matrix from the complex coefficients, theoretically calculated from the Fourier transform of the output intensity. As calibration parameters, the initial orientations of the polarizer-analyzer are used. Experimental results for air and a rotating dichroic film polarizer show our proposal's feasibility.

Highly Efficient Double Microprism Polarizer with Microstructured Molecular Ordering

AbstractUsing crafted microstructures with complex molecular ordering has proven to be an excellent approach to control the propagation and phase front of light, and consequently, has led to remarkable advances in various photonic devices. A polarization‐conversion‐type polarizer with extraordinarily high transmittance can be another innovative photonic application that can be realized using microfabricated molecular ordering; however, the technology is still at the stage of idea generation. Here, a novel polarization conversion polarizer is demonstrated using a polymerized liquid crystalline double microprism (DMP) array and patterned retarder. A lab‐made polarizer using the method exhibits the degree of polarization of 94.5% without absorption or large reflection of light, and its transmittance is found to be ≈1.8 times higher than a dichroic sheet polarizer. In addition, the DMP polarizer works in the full spectral range of visible light and its thickness is less than 150 µm; therefore, it can be used in flat photonic devices, including displays. DMP polarizers can easily be fabricated using well‐established soft lithography and photoalignment methods. Thus, the proposed technology can open new possibilities for polymerized liquid crystal films with well‐crafted molecular ordering.

Dichroic Circular Polarizers Based on Plasmonics for Polarization Imaging Applications.

Dichroic circular polarizers (DCP) represent an important group of optical filters that transfer only that part of the incident light with the desired polarization state and absorb the remainder. However, DCPs are usually bulky and exhibit significant optical loss. Moreover, the integration of these kinds of DCP devices can be difficult and costly as different compositions of chemicals are needed to achieve the desired polarization status. Circular polarizers based on metasurfaces require only thin films in the order of hundreds of nanometers but are limited by their sensitivity to angle of incidence. Furthermore, few existing solutions offer broadband operation in the visible range. By using computational simulations, this paper proposes and analyses a plasmonic DCP structure operating in the visible, from 400 nm to 700 nm which overcomes these drawbacks. The resulting circular dichroism transmission (CDT) is more than 0.9, and the maximum transmission efficiency is greater than 78% at visible wavelengths. These CDT characteristics are largely independent of angle of incidence up to angles of 80 degrees.

Luminescent Liquid Crystals Based on Carbonized Polymer Dots and Their Polarized Luminescence Application.

Traditional luminescent liquid crystals (LLCs) suffer from fluorescence quenching caused by aggregation, which greatly limits their further application. In this work, a kind of novel LLCs (named carbonized polymer dot liquid crystals (CPD-LCs)) are designed and successfully synthesized through grafting the rod-shaped liquid crystal (LC) molecules of 4'-cyano-4-(4″-bromohexyloxy) biphenyl on the surface of CPDs. The peripheral LC molecules not only increase the distance between different CPDs to prevent them from aggregating and reduce intermolecular energy resonance transfer but also make this LLC have an ordered arrangement. Thus, the obtained CPD-LCs show good LC property and excellent high luminous efficiency with an absolute photoluminescence quantum yield of 14.52% in the aggregated state. Furthermore, this kind of CPD-LC is used to fabricate linearly polarized devices. The resultant linearly polarized dichroic ratio (N) and polarization ratio (ρ) are 2.59 and 0.44, respectively. Clearly, this type of CPD-LC shows promising applications for optical devices.

19.1: Synthesis and Spectral Quality of Flexible Display Dichroic Dye Polarizer

SID Symposium Digest of Technical PapersVolume 52, Issue S1 p. 126-126 Technical Sessions: Session 19: High Perceptive LC Display Technologies (Liquid Crystal Technology)Free to Read 19.1: Synthesis and Spectral Quality of Flexible Display Dichroic Dye Polarizer Xiaolian Li, Corresponding Author Xiaolian Li xlianli@dlut.edu.cn State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, ChinaSearch for more papers by this authorRouchen Pan, Rouchen Pan State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, ChinaSearch for more papers by this author Xiaolian Li, Corresponding Author Xiaolian Li xlianli@dlut.edu.cn State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, ChinaSearch for more papers by this authorRouchen Pan, Rouchen Pan State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, ChinaSearch for more papers by this author First published: 24 February 2021 https://doi.org/10.1002/sdtp.14402AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume52, IssueS1International Conference on Display Technology (ICDT 2020)February 2021Pages 126-126 RelatedInformation

Experimental and Theoretical Studies on Sustainable Synthesis of Gold Sol Displaying Dichroic Effect.

Gold nanoparticles depending on their shape and mixtures of multiple shapes can exhibit peculiar optical properties, including the dichroic effect typical of the Lycurgus cup, which has puzzled scientists for a long time. Such optical properties have been recently exploited in several fields such as paint technology, sensors, dichroic polarizers, display (LCD) devices, laser applications, solar cells and photothermal therapy among others. In this article, we have demonstrated a simple room temperature one-pot synthesis of gold sol displaying a dichroic effect using a slow reduction protocol involving only trisodium citrate as a reducing agent. We found that the dichroic gold sol can be easily formed at room temperature by reducing gold salt by trisodium citrate below a certain critical concentration. The sol displayed an orangish-brown color in scattered/reflected light and violet/blue/indigo/purple/red/pink in transmitted light, depending on the experimental conditions. With minor changes such as the introduction of a third molecule or replacing a small amount of water in the reaction mixture with ethanol, the color of the gold sol under transmitted light changed and a variety of shades of red, pink, cobalt blue, violet, magenta and purple were obtained. The main advantage of the proposed method lies in its simplicity, which involves the identification of the right ratio of the reactants, and simple mixing of reactants at room temperature with no other requirements. TEM micrographs displayed the formation of two main types of particles viz. single crystal gold nanoplates and polycrystalline faceted polyhedron nanoparticles. The mechanism of growth of the nanoplates and faceted polyhedron particles have been described by an enhanced diffusion limited aggregation numerical scheme, where it was assumed that both trisodium citrate and the gold ions in solution undergo a stochastic Brownian motion, and that the evolution of the entire system is regulated by a principle of energy minimization. The predictions of the model matched with the experiments with a good accuracy, indicating that the initial hypothesis is correct.

Dichroic Polarizing Metasurfaces for Color Control and Pseudo-Color Encoding

In ultracompact image displays based on metasurfaces, the image color is usually controlled by varied nanostructure dimensions, which requires elaborate design and precise manufacturing of nanostructures. Here, we present a metasurface composed of equal-sized nanostructures to control the color of output light, simply by polarization control. Specifically, with resonances occurring in two orthogonal axes for different wavelengths, each nanostructure of the metasurface acts as a biaxial nano-polarizer and reflect most of incident red and green light polarized along the long and short axes, respectively. Hence, by means of reconfiguring the orientations of the biaxial nano-polarizers, the mixture of red and green light with different intensity ratio, governed by Malus law, can be employed to generate a pseudo-colored nanoprinting image. We experimentally demonstrate the proposed metasurfaces by successfully encoding and decoding pseudo-color nanoprinting images right at the metasurfaces. With advantages such as flexible image display and ultra-simple nanostructure design, the proposed dichroic polarizing metasurface can promote advanced research of metasurfaces in color control, ultracompact image display, pseudo-color processing, and many other related fields.

Laser stabilization to neutral Yb in a discharge with polarization-enhanced frequency modulation spectroscopy

Isotope selective optical excitation of atoms is important for experiments with neutral atoms, metrology, and work with trapped ions, including quantum information processing. Polarization-enhanced absorption spectroscopy is used to frequency stabilize a tunable external cavity laser diode system at 398.9 nm for isotope selective photoionization of neutral Yb atoms. This spectroscopy technique is used to measure isotope resolved dispersive features from transitions within a see-through configuration ytterbium hollow-cathode discharge lamp. This Doppler-free dichroic polarization spectroscopy is realized by retro-reflecting a laser beam through the discharge and analyzing the polarization dependent absorption with balanced detection. The spectroscopy signal is recovered using lock-in detection of frequency modulation induced by current modulation of the external cavity laser diode. Here, we show an order of magnitude improvement in the long-term stability using polarization-enhanced absorption spectroscopy of Yb compared to polarization spectroscopy.

Molecular Ordering Behavior of Lyotropic Chromonic Liquid Crystals on a Polyimide Alignment Layer

Coating-type polarizing films with high dichroic ratio (DR) and polarization efficiency in the visible region were fabricated using a solution of ternary lyotropic chromonic liquid crystals (LCLCs). Optical characteristics of these anisotropic LCLC polarizing films were then determined. DR increased with increasing LCLC concentrations. Molecular ordering of these LCLCs on a rubbed polyimide (PI) layer increased because LCLC molecules' orientation was enhanced by the dielectric anisotropy effect from rubbing the surface of the PI. In addition, this study demonstrated how the interaction between liquid crystal aggregates and the PI surface with different LCLC solutions correlated with LCLC molecular orientations on the PI which significantly depended on whether the coating direction of the LCLC solution was parallel or perpendicular to the PI rubbing direction. It was found that ordering direction at high LCLC concentrations was determined by shearing direction of the LCLC solution coating whereas the ordering direction at low LCLC concentrations was governed by the dielectric anisotropy effect from PI rubbing direction.

Fabrication and optical properties of dichroic polarizing films based on poly(vinyl alcohol)-heteropolyacid nanocomposites

We report on a new type of poly(vinyl alcohol)(PVA)-based dichroic polarizing films whose visible dichroism is due to long-chain linear polyenes, –(CH=CH)n–, formed in the course of acid-catalyzed thermal dehydration of the polymer. The distinguishing feature of these films is that the solid acid catalyst (12-tungstophosphoric acid, TPA) is used instead of the liquid ones. Thin PVA films with embedded TPA nanoparticles were fabricated by solution casting technique. Subsequent stretching and annealing of these PVA/TPA nanocomposites produced PVA–polyene/TPA dichroic polarizing films with the thickness below 10 µm. Transmission electron microscopy, Fourier-transform infrared spectroscopy, and UV–Vis spectroscopy techniques were used to characterize the films at various stages of preparation. The fabricated polarizing films showed polarization efficiency exceeding 94% and transmittance higher than 40% in the visible range. The polarizing properties of the films did not deteriorate upon prolonged exposures to hot humid air (60 °C, 90% RH) and high temperature (90 °C). The nanocomposite polarizing film proposed in this study may have application potential in thin and flexible optoelectronic devices that must operate under harsh environmental conditions.

Laser-induced gratings in Ag3AsS3 semiconductors

We demonstrated experimentally an opportunity to form space grating patterns in Ag3AsS3 semiconductor crystals under an influence of coherent femtosecond (195 fs) laser beams. The observation of the laser stimulated gratings has been performed using a cw He–Ne laser with power about 15 mW at 1150 nm wavelength. The photoinducing femtosecond laser with pulse duration about 190 fs and frequency 65 MHz bandpass has been used in the two-beam coherent regime at wavelength 1045 nm. The set of dichroic mirrors, polarizers, and lenses have been applied to form two space-separated beams, which interact with the studied Ag3AsS3 trigonal single crystals. The treatment has been performed during additionally applied dc-electrical strength equal to about 8 kV/cm with a frequency about 20 kHz directed perpendicularly to the optical axis. The monitoring of the photo-thermal effects and photo-destruction have been done using the optical fiber spectrometer Ocean Optics with spectral resolution 1 nm.

Simple undergraduate experiment for synthesizing and analyzing non-uniformly polarized beams by means of a Fresnel biprism

A simple scheme to synthesize non-uniform patterns of polarization across the transverse section of a beam is proposed with the standard materials in an undergraduate optics laboratory. The experiment is based on the superposition of two orthogonally polarized fields obtained by using a Fresnel biprism and dichroic polarizers. Although no interference pattern appears in the superposition area, a non-uniformly totally polarized field is synthesized. Analytic expressions for the Jones vector and Stokes parameters of the output beam are calculated and, in the process, students can cement their knowledge about the representation of polarized light with these formalisms. The experimental polarization pattern is either obtained from intensity measurements with a CCD camera or measured directly with a commercial polarimeter modified with a pinhole. This experiment will help students discover an easy way to vary the state of polarization across the transverse section of a light field.

3D-printed chiral metasurface as a dichroic dual-band polarization converter.

We propose a novel design of a 3D chiral metasurface behaving as a spatial polarization converter with asymmetric transmission. The metasurface is made of a lattice of metallic one-and-a-half-pitch helical particles. The proposed metasurface exhibits a dual-band asymmetric transmission accompanied by the effect of complete polarization conversion. Regarding circularly polarized waves, the metasurface demonstrates a strong circular dichroism. A prototype of the metasurface is manufactured for the quasi-optic experiment by using a 3D printing technique utilizing a cobalt-chromium alloy, which exhibits good performances against thermal fatigue and corrosion at high temperatures.

Macroscopic Alignment of Silver Nanoplates in an Adaptable Dichroic Polarizer

Morphological control to precisely tailor the energy absorption bands of plasmonic particles is improving constantly, with efforts to improve the monodispersity of the designed particles leading to sharper plasmonic features in controlled spectral regions. Transitioning these highly tailored plasmonic additives into a robust polymer composite platforms while retaining their specified plasmonic features has proven challenging, with the elevated temperatures and mechanical forces involved in composite manufacturing resulting in particle agglomeration and morphology alterations. In this work, thermally stable protecting layers are developed onto tailored silver nanoplate (Ag-NPL) plasmonic additives to facilitate their survivable processing at elevated temperature. The produced coatings allow for their implementation in a facile, low-cost method to produce uniform dichroic optical polarizers based on the protected Ag-NPLs in a polymer matrix. Nanocomposites are obtained through an extrusion and injection molding process, which is shown to induce alignment of anisotropic particles based on sheer forces. As the optical position of the resonances is dependent on the morphology of the additive, and unlike other methods where the anisotropy in the NP is induced in situ, our method can be easily adapted to varying optical regimes by modifying the size and shape of the initial additive. Furthermore, the method presented in this work forgoes the need for a polymer stretching alignment mechanism which enables the ability to use various types of anisotropic particles with visible and near-infrared operating regimes.

Novel Photoalignment Method Based on Low-Molecular-Weight Azobenzene Dyes and Its Application for High-Dichroic-Ratio Polarizers.

Photoalignment is a simple technique for the manipulation of molecular orientations, which has been widely used in liquid crystal displays. Here, we propose a novel photoalignment method, in which an azobenzene dye thin film is deposited by thermal evaporation and in situ exposed to linearly polarized light simultaneously. We obtain polarizers with a dichroic ratio of up to 62, which is the highest value ever realized by a photoalignment method. Moreover, the polarizing thin film has a thickness of just 200 nm, compatible with flexible substrates, making it perfect for use as a dichroic polarizer in ultrathin and flexible displays.

Distortion of Magnetic Fields in a Starless Core II: 3D Magnetic Field Structure of FeSt 1-457

Abstract Three-dimensional (3D) magnetic field information on molecular clouds and cores is important for revealing their kinematical stability (magnetic support) against gravity, which is fundamental for studying the initial conditions of star formation. In the present study, the 3D magnetic field structure of the dense starless core FeSt 1-457 is determined based on the near-infrared polarimetric observations of the dichroic polarization of background stars and simple 3D modeling. With an obtained angle of line-of-sight magnetic inclination axis of and previously determined plane-of-sky magnetic field strength of 23.8 ± 12.1 , the total magnetic field strength for FeSt 1-457 is derived to be 33.7 ± 18.0 . The critical mass of FeSt 1-457, evaluated using both magnetic and thermal/turbulent support is , which is identical to the observed core mass, . We thus conclude that the stability of FeSt 1-457 is in a condition close to the critical state. Without infalling gas motion and no associated young stars, the core is regarded to be in the earliest stage of star formation, i.e., the stage just before the onset of dynamical collapse following the attainment of a supercritical condition. These properties could make FeSt 1-457 one of the best starless cores for future studies of the initial conditions of star formation.

On the behavior of degree of polarization surfaces at the limit of Poincaré sphere walls

Recently a new class of mathematical entities—the gyrovectors—came into light in physics. The most intuitive examples of gyrovectors are the relativistic allowed velocities and the Poincare polarization vectors. Taking advantage of the (also recently elaborated) approach of degree of polarization surfaces in polarization theory, I make an analysis of the strange behavior of these entities in the interaction between the polarized light and the orthogonal dichroic polarization devices. The same approach can be applied in the theory of relativity as well as in many other branches of optics (multilayer optics, ray optics, laser cavity physics, quantum optics) where the Lorentzian character of the transformations which govern some specific problems has been recognized.