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In-plane anisotropic two-dimensional (2D) materials, emerging as an intriguing type of 2D family, provide an ideal platform for designing and fabrication of optoelectronic devices. Exploring air-stable and strong in-plane anisotropic 2D materials is still challenging and promising for polarized photodetection. Herein, SiP2, a 2D IV-V semiconductor, is successfully prepared and introduced into an in-plane anisotropic 2D family. The basic characterizations combined with theoretical calculations reveal 2D SiP2 to exhibit an intrinsically low-symmetry structure, the in-plane anisotropy of phonon vibrations, and an anisotropically dispersed band structure. Moreover, the photodetector based on 2D SiP2 exhibits high performance with a high detectivity of 1012 Jones, a large light on/off ratio of 103, a low dark current of 10-13 A, and a fast response speed of 3 ms. Furthermore, 2D SiP2 demonstrates a high anisotropic photodetection with an anisotropic ratio up to 2. In addition, the polarization-sensitive photodetector presents a dichroic ratio of 1.6 due to the intrinsic linear dichroism. These good characteristics make 2D SiP2 a promising candidate as an in-plane anisotropic semiconductor for high-sensitivity and polarized optoelectronic applications.

In this article authors present a prototype of a dichroic scanning nonlinear optical microscope with a photodetecting polymer Scanner and a customized objective lens with an external back focal plane. Two types of two-axis electromagnetic actuated polymer scanners are manufactured by a standard printed circuit board (PCB) fabrication process. Both scanners share the same overall dimensions of 45 mm by 45 mm. The maximum optical scan angle of a type I scanner is 13 degrees at 420 Hz by the fast axis in resonance and 4 degrees by the slow axis in the linear mode. The type II scanner shows similar performance. A scan lens as well as a tube lens in a conventional nonlinear optical microscope are replaced by placing such a polymer scanner on the external back focal plane of a customized water immersion objective lens. The objective lens has the back working distance of 6 mm, the numerical aperture of 0.7, the front working distance of 1.16 mm, a field of view of 1.67 mm in the diameter and the angle of view of +/−15 degrees. Preliminary imaging results are also presented.

Ali CMB Polarization Telescope (AliCPT) is the first Cosmic Microwave Background (CMB) polarimeter with a large focal plane camera to be deployed in the Northern Hemisphere, in the Tibetan Plateau. Here we present the design of a dichroic (90/150 GHz) focal plane camera capable of hosting up to 32,376 Transition-Edge Sensor (TES) bolometers operating from a base temperature of 280 mK. Detectors are fabricated as monolithic arrays of 1,704 feedhorn-coupled and polarization-sensitive TES bolometers that are packaged in independent modules and read out with a microwave multiplexing architecture. A custom RFSoC-based system manages the multiplexing readout. Prototype AliCPT pixels have been fabricated and characterized, demonstrating passband performance within 2.5% of design and cross-polarization systematic sensitivity $\leq$ 2%.

Polarization-sensitive photodetector based on low-dimensional semiconductor is a kind of special photoelectric device which can take advantage of the semiconductor’s anisotropy and convert it into an electrical signal. However, the polarization performance of the photodetector is limited by the challenges of the anisotropy of semiconductors. The design of alloy semiconductors with excellent anisotropy is one of the mainstream methods to improve the dichroic ratio of the polarization-sensitive photodetector. Here, we design the tunable alloying Sb–S–Se nanowires (NWs), which can be used in the research field of polarization-sensitive photodetectors because of their low symmetry crystal structure, suitable bandgap, and high mobility. It is demonstrated that the metal-semiconductor-metal polarization-sensitive photodetector based on Sb–S–Se NWs has great photoelectric properties and polarization performance in UV–Vis-near-infrared response (NIR) spectrum. Under the irradiation laser of the 532-nm, the photoresponsivity ( ${R}$ ) and detectivity ( ${D}$ *) of the Sb2(S1/3Se2/3)3 NW-based polarization-sensitive photodetector can reach 6.38 A/W and 1.63 $\times 10^{9}$ Jones. By investigating the polarization characteristics of the photodetector, the dichroic ratio of the photodetector can reach 3.8 at 532 nm. By regulating the proportion of each component in the alloy semiconductor, an effective method is provided for adjusting the photoresponse spectrum and optimizing the performance of the polarization-sensitive photodetector, which has a promising research prospect in the future.

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.

Two-dimensional (2D) organic-inorganic hybrid perovskites, benefiting from their natural anisotropy of quantum-well motifs and optical properties, have shown remarkable polarization-dependent responses superior to the 3D counterparts. Here, for the first time, multiwavelength polarization-sensitive detectors were fabricated by using single crystals of a guanidine-based 2D hybrid perovskite, (BA)2 (GA)Pb2 I7 (where BA+ is n-butylammonium and GA+ is guanidium). Its unique 2D quantum-well structure results in strong crystallographic-dependence of optical absorption. Strikingly, our crystal-based photodetector exhibits a prominent photocurrent dichroic ratio (Imax /Imin ) of ∼2.2 at 520 nm, higher than the typical 2D inorganic materials (GeSe, ∼1.09, PdSe2 , ∼1.8). In addition, notable dichroic ratios of 1.29 and 1.23 at 405 nm and 637 nm are also created for the multiwavelength polarized-light detection. The prominent detecting performances, including low dark current (1.6×10-11 A), considerable on/off ratio (∼2×103 ), high photodetectivity (∼3.3×1011 Jones) and responsivity (∼12.01 mA W-1 ), make (BA)2 (GA)Pb2 I7 a promising candidate for polarized-light detection. This work sheds light on the rational engineering of new 2D hybrid perovskites for the high-performance optoelectronic device applications.

The near-infrared (NIR) polarized photodetector has wide range of applications including the object identification. Wavelength of 1550 nm is the least loss band for transmission communication, and the study of photodetectors working at 1550 nm demonstrate special scientific and applied significances. GaSb has attracted tremendous attention in the field of photoelectric detection due to its suitbale band gap, high mobility, sensitivity, and good compatibility with modern microelectronics technology. In this work, a highly polarization-sensitive GaSb nanowire-based photodetectors under short-wave near-infrared photoelectric detection is achieved. The device has a good optical detection ability in the near-infrared band, and showed the responsivity up to 77.3 A/W with the external quantum efficiency of $6.18\times 10 ^{3}$ % (illumination intensity of 1.59 mW/mm2) under 1550 nm. Furthermore, obvious photocurrent anisotropy are investigated under the near-infrared band from 808 nm to 1550 nm. The largest dichroic ratio reaches 3.3 at 1550 nm. These results indicate that GaSb nanowire based photodetectors are not only promising candidates for NIR detection but also have promising potentials in polarization sensitive applications.

Integrating conventional optics into compact nanostructured surfaces is the goal of flat optics. Despite the enormous progress in this technology, there are still critical challenges for real-world applications due to the limited operational efficiency in the visible region, on average lower than 60%, which originates from absorption losses in wavelength-thick (≈ 500 nm) structures. Another issue is the realization of on-demand optical components for controlling vectorial light at visible frequencies simultaneously in both reflection and transmission and with a predetermined wavefront shape. In this work, we developed an inverse design approach that allows the realization of highly efficient (up to 99%) ultrathin (down to 50 nm thick) optics for vectorial light control with broadband input–output responses in the visible and near-IR regions with a desired wavefront shape. The approach leverages suitably engineered semiconductor nanostructures, which behave as a neural network that can approximate a user-defined input–output function. Near-unity performance results from the ultrathin nature of these surfaces, which reduces absorption losses to near-negligible values. Experimentally, we discuss polarizing beam splitters, comparing their performance with the best results obtained from both direct and inverse design techniques, and new flat-optics components represented by dichroic mirrors and the basic unit of a flat-optics display that creates full colours by using only two subpixels, overcoming the limitations of conventional LCD/OLED technologies that require three subpixels for each composite colour. Our devices can be manufactured with a complementary metal-oxide-semiconductor (CMOS)-compatible process, making them scalable for mass production at low cost.

We report complex optical investigations of polymer-stabilised cholesteric photonic liquid crystal doped by a dichroic fluorescent dye. For the first time, we employed a combination of various expe...

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.

With the fast development of semiconductor technology, self-driven devices have become an indispensable part of modern electronic and optoelectronic components. In this field, in addition to traditional Schottky and p–n junction devices, hybrid 2D/3D semiconductor heterostructures provide an alternative platform for optoelectronic applications. Herein we report the growth of 2D SnS1−xSex (x = 0, 0.5, 1) nanosheets and the construction of a hybrid SnS0.5Se0.5/GaAs heterostructure based self-driven photodetector. The strong anisotropy of 2D SnS1−xSex is demonstrated theoretically and experimentally. The self-driven photodetector shows high sensitivity to incident light from the visible to near-infrared regime. At the wavelength of 405 nm, the device enables maximum responsivity of 10.2 A W−1, high detectivity of 4.8 × 1012 Jones and fast response speed of 0.5/3.47 ms. Impressively, such a heterostructure device exhibits anisotropic photodetection characteristics with the dichroic ratio of ∼1.25 at 405 nm and ∼1.45 at 635 nm. These remarkable features can be attributed to the high-quality built-in potential at the SnS0.5Se0.5/GaAs interface and the alloy engineering, which effectively separates the photogenerated carriers and suppresses the deep-level defects, respectively. These results imply the great potential of our SnS0.5Se0.5/GaAs heterostructure for high-performance photodetection devices.

FSS provides enormous applications such as radomes, stealth technology, dichroic sub-reflector, photonic sub-reflector, military applications, antenna Technology and earth observing remote sensing instruments. Apart from this, Electromagnetic Interference shielding is the hottest research area due to advancement of mobile communication technology. The growing radiations from these mobile communication can be suppressed by transforming entire or aperture of wall in to FSS surface to protect highly sensitive equipment and human from health hazards. So this article presents the basics concepts, types and challenges of FSS especially for EMI shielding application and its theoretical investigations. Hence the various stop band filters have analyzed particularly in terms of unit cell dimension, element type and angular stability. Apart from these, tunable FSS are also discussed.

The attractive optical properties of metallic nanoparticles include the optically interesting but surprisingly not well understood dichroic effect, defined in this research as when particle colloids display different colours in transmitted and reflected light. Here we use a systematic experimental approach supplemented by theoretical Mie theory analysis to study the origin of this effect. The CloudSpec spectrophotometer has been utilised to produce quantitative scattering and absorption spectra for monodisperse spherical gold nanoparticles, allowing precise links to be made between the optical spectra and the colours observed. The source of the dichroic effect has been conclusively linked to particle size with no special particle shapes or size distributions required. These results experimentally demonstrate the relationship between particle size and the ratio of scattering to absorption predicted by Mie theory, which has important implications for users of Mie theory calculations.

Polarimetry in the far ultraviolet (FUV) is a powerful tool in many applications such as UV/EUV ellipsometry, characterization and control of the beam polarization status in large scale facilities and solar physics. FUV polarizers are among the most difficult components to manufacture, mainly due to the lack of dichroic and transparent materials in this spectral range. Although many different solutions for their fabrication have been investigated in the last decades, surprisingly, the use of Wire Grid Polarizers (WGPs) is still poorly investigated in this spectral region. In this work, two different concepts of WGPs have been designed and optimized for the FUV range: one is based on absorptive nano-wires on top of an highly reflective substrate, and the second one is based on highly reflective nano-wires on top of an absorptive substrate. Different wires' shapes have been considered and relative structures optimized at a target wavelength of 121.6 nm. Two very promising solutions have been selected, which exhibit a polarization degree over 99.9% and a TE-reflectance over 0.2. Their sensitivity to the wires' dimension parameters have been investigated to assess their feasibility.

In this work, we report the design, construction,and characterization of two free-standing single-layer frequencyselective surface structures to be used as dichroic filters in theTHz range. Their spectral responses are aimed to fulfill a stringent band-pass performance in the atmospheric window between600 and 725 GHz. Specifically, the dichroics have been required toallow a transmission of electromagnetic radiation of at least 90%,achieve a rejection in the stop-band lower than −25 dB, and havecross-polarization levels below −30 dB. All these specificationswere demanded to be satisfied at normal and nonnormal beamincidence. We have studied dichroic filters with hexagonal patternsof two different apertures, a well-known single-hole geometry and,in order to enhance the spectral performance, a novel aperturegeometry that we call the flower type. Their transmission characteristics were measured using a Fourier transform spectrometer.The electromagnetic simulations and experimental results not onlyshow a good agreement but they demonstrate that the flowertype geometry can greatly outperform its single-hole counterpartachieving all the desired requirements. In this way, we demonstratethe feasibility of implementing single-layer systems at (sub)-THzfrequencies suitable for low-noise astronomical applications.

Multifunctional flexible Au electrodes based on one-dimensional (1D) arrays of plasmonic gratings are nanofabricated over large areas with an engineered variant of laser interference lithography optimized for low-cost transparent templates. Au nanostripe (NS) arrays achieve sheet resistance in the order of 20 Ohm/square on large areas (∼ cm2) and are characterized by a strong and dichroic plasmonic response which can be easily tuned across the visible (VIS) to near-infrared (NIR) spectral range by tailoring their cross-sectional morphology. Stacking vertically a second nanostripe, separated by a nanometer scale dielectric gap, we form near-field coupled Au/SiO2/Au dimers which feature hybridization of their localized plasmon resonances, strong local field-enhancements and a redshift of the resonance towards the NIR range. The possibility to combine excellent transport properties and optical transparency on the same plasmonic metasurface template is appealing in applications where low-energy photon management is mandatory like e.g., in plasmon enhanced spectroscopies or in photon harvesting for ultrathin photovoltaic devices. The remarkable lateral order of the plasmonic NS gratings provides an additional degree of freedom for tailoring the optical response of the multifunctional electrodes via the excitation of surface lattice resonances, a Fano-like coupling between the broad localised plasmonic resonances and the collective sharp Rayleigh modes.

Linear dichroism is an important tool to characterize the transmission matrix and determine the crystal or orbital orientation in a material. In order to achieve high-resolution mapping of transmission properties, the linear-dichroism scattering model in ptychographic imaging is introduced, and an efficient two-stage reconstruction algorithm is developed. Using the proposed algorithm on a uniaxial material, the dichroic transmission matrix can be recovered without an analyzer by using ptychography measurements with as few as three different polarization angles, with the help of an empty region to remove phase ambiguities.

We designed and synthesized new smectic liquid crystalline monomers containing photopolymerizable acrylate groups and a mesogenic core unit composed of two benzene rings, one pyrimidine-based heteroaromatic ring and an acetylene linking group. The structures of monomers were characterized by 1H nuclear magnetic resonance spectroscopy, and their mesomorphic behaviors were investigated by differential scanning calorimetry and polarized optical microscopy. Both of monomers showed an enantiotropic phase transition behavior with exhibiting both nematic phase and highly ordered smectic phase. Both of monomers showed smectic phases during the cooling process in the temperature range of 144.2–94.0 °C and 154.0–85.8 °C, respectively. Neither of these compounds showed a homogeneous alignment even at various temperatures, and therefore, their 50:50 mixture was chosen for the preparation of guest-host mixture because of its lowest crystallization point, wide smectic phase temperature range and superior aligning property. Polymerizable “host-guest” mixture formulated from the host liquid crystalline monomer mixture, dichroic dye and additives was injected into the sandwiched glass substrates having rubbed alignment layers at the isotropic temperature. Subsequent in-situ photopolymerization by UV irradiation at room temperature successfully resulted in a thin film polarizer with good polarizing properties. The fabricated guest-host polarizer showed a dichroic ratio (DR) of 13.1 and a degree of polarization (DOP) of 95.5% with the thickness of 5 µm.

Coating-type polarizing films with a 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 is significantly dependent on whether the coating direction of the LCLC solution was parallel or perpendicular to the PI rubbing direction. It was found that the 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 the PI rubbing direction.

The extraordinary optical and electronic properties of anisotropic two-dimensional materials, such as black phosphorus, ReS2, and GeSe, enable them a promising component of polarization-sensitive photodetectors. However, these applications are significantly limited by the challenges of air-stability, response time, and linearly dichroic ratio. Interestingly, palladium diselenide (PdSe2) with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure. We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation, and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements. Such unique linear dichroism, endows the PdSe2 photodetector powerful ability to detect polarized light. The photodetector based on 5L PdSe2, as tested with polarization-dependent photocurrent mapping, exhibited competitive capability to detect polarized light, achieving a significant photocurrent on/off ratio (> 102), the quite fast response time (< 11 ms) and robust linearly dichroic ratios (/max//min ≈ 1.9 at 532 nm). These results are essential advance in the development of polarization-sensitive photodetector, a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.

We revealed the mechanism of circular dichroic inversion of cellulosic/polymer cholesteric liquid crystalline (ChLC) composites induced by applying compressive stress through a modeling approach. W...

The design and synthesis of an enantiomeric pair of 1,8-diethynylanthracene-bridged naphthalenediimide (NDI)-based cyclophanes (Cyclo-NDIs) are reported. Each enantiomer of Cyclo-NDI exhibits a circularly polarized luminescence signal with a relatively large luminescence dissymmetry factor (glum =±8×10-3 ). We have further investigated the modulation of through-space electronic communication between co-facially oriented NDIs in a discrete Cyclo-NDI with changes in the temperature. Tuning of the electronic communication results from the conformational transformation of monomer- versus dimer-like features of Cyclo-NDI, as confirmed by UV/Vis, fluorescence, circular dichroic, and NMR spectroscopic analysis. The temperature-dependent optical response in the Cyclo-NDI through the conformational transformation could be utilized as a highly sensitive and reversible optical thermometer in a wide temperature range (100 to -80 °C).

Dichroic organic films have found a broad application in various optoelectronic devices. One efficient method for the production of thin dichroic films is the deposition of the film onto aligning polymer surface. Scientists propose different explanations concerning the mechanisms of the molecules aligning. Here, we report the aligning of squaraine (Sq) molecules on the different aligning polymer surfaces, independent from the morphology of the Sq deposits. Aligned polytetrafluoroethylene (PTFE) layers were produced by either unidirectional hot friction transfer or by PTFE decomposition in vacuum with the activation of the gas by accelerated electrons and the consequent unidirectional rubbing with a cloth. Sq films grown on the aligned PTFE surfaces and on the nanostructured polycarbonate (PC) surfaces were found to exhibit dichroic optical absorption spectra. Despite different shape and orientation of the Sq crystals on the PTFE and the PC surfaces, the absorption of polarized light was shown to exhibit one pattern. Variations in the morphology of Sq films on different surfaces were explained by the competitive participation of different growth mechanisms, which depended on the properties of the deposited compound, the aligning layer and the growth conditions. The PTFE aligning layers can be useful in organic electronics due to low-temperature processing.

The circular dichroism spectra of a single chain of polyfluorene was predicted for a p-twisted helix conformation and local planarized polymer sections in the presence and in the absence of thermal vibrations. Under thermal vibrations at 300 K, the planarized section of polyfluorene affords a red-shifted positive dichroic band between 446 and 456 nm, preserving a degree of chirality. The S1

The Simons Observatory will measure the cosmic microwave background temperature and polarization using a suite of new telescopes in the Atacama Desert in Chile. The Simons Observatory will use dichroic transition edge sensor (TES) bolometer arrays spanning six frequency bands from 27 to 280 GHz. The Simons Observatory will pioneer the use of a densely packed multiplexing architecture based on the microwave SQUID multiplexer ($$\mu $$mux), housing $$\sim \! 2000$$ microwave resonators, each coupled to a TES. The Simons Observatory aims to multiplex each array of $$\sim \! 2000$$ detectors with a single pair of coaxial cables and requires a multiplexing factor of $$\sim \! 1000$$. The Simons Observatory cryogenic readout system is called the universal microwave multiplexing module (UMM). The UMM couples to both horn and lenslet-coupled detector arrays and is integrated into the universal focal-plane module (UFM) after being independently characterized. We present processes we have developed for highly repeatable and automated integration methods of UMMs, which will be needed for the production of the 49 UFMs required for the first stage of the Simons Observatory.

Surface topography variations of liquid crystal networks in their functional coatings provide unique properties in these systems. Chiral-nematic polymer coatings self-organize in a fingerprint texture with the molecular helices parallel to the substrate with alternating domains of molecular units with parallel and perpendicular director orientation as controlled by the concentration of a reactive chiral additive. Driven by surface-tension differences and altered by anisotropic polymerization shrinkage, the coating may form hills and valleys hundreds of nanometers in size with different molecular alignment. The director orientation in the corrugations could be controlled by monomer diffusion during polymerization. Polymerization in the presence of a dichroic dye gives topographic elevations in which the molecules are oriented along the normal. Polymerization by means of a dichroic photoinitiator gives topographic elevations in which the molecules align parallel to the surface. By balancing the monomer diffusion and anisotropic polymerization shrinkage, relatively flat surfaces are also achieved. The different surfaces exhibit distinct topographical deformations when subjected to external stimuli, such as an AC electric field. This method can be universally extended to LC polymers with other alignment configurations.

Polarization conversion dichroism is of particular interest in manipulating the polarization state of light, whereas high-performance asymmetric transmission (AT) of linearly polarized waves is still inaccessible in the terahertz range. Here, a bilayer chiral metamaterial consisting of orthogonally chained S-shaped patterns with broken symmetry along the light propagation direction is proposed and demonstrated experimentally to realize a dual-band dichroic AT effect for linearly polarized terahertz waves. The AT effects are robust across a wide range of incident angles. The observed strong AT can be theoretically explained by a multiple reflection and transmission interference model and the transfer matrix method. The proposed bilayer chiral metamaterial may have broad applications in polarization manipulation, chiral biosensing and direction-dependent information processing.

By dimensional reduction of the 3D motif of Cs2 AgBiBr6 , a lead-free 2D hybrid double perovskite, (i-PA)2 CsAgBiBr7 (1, i-PA=isopentylammonium), was successfully designed. It adopts a quantum-confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio αb /αc =1.9 at 405 nm). Such anisotropy attributes result in the strong polarization-sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization-sensitive materials.

High-efficiency linearly polarized luminescence (LPL) materials are very important for display equipment and optical apparatus. Herein, we construct a free-standing film with a wavelength-tunable LPL property through the luminescent material. First, a highly efficient fluorescent reactive monomer (M6BP) based on α-cyanostilbene with stimuli-responsive behavior is successfully designed and synthesized. Then, the free-standing film is prepared by photo polymerizing the mixture of M6BP and liquid crystal (LC) monomer (C6M) in an antiparallel lab-made LC cell. The resultant film achieves a uniaxial orientation along the polyvinyl alcohol (PVA) substrate rubbing direction, which endows it with good LPL behavior. The dichroic ratio (N) and polarization ratio (ρ) values of the film are measured as 2.63 and 0.45, respectively. Owing to the existence of the pyridine group, the resultant film exhibits a reversible fluorescence switch with LPL property under trifluoroacetic acid (TFA)/triethylamine (TEA) vapors. Furthermore, a film with a special orientation pattern is obtained by photoalignment, and it is further successfully applied in the anti-counterfeiting field. This work provides a new method to fabricate optical devices with wavelength-tunable LPL property.

The Lycurgus cup is worldwide admired in particular because of its fascinating dichroic property. The cup presents a green colour when the observer and the light source are on the same side (reflection), and a deep red colour when the observer and the light source are at opposite sides (transmission). This peculiar effect, which has perplexed scientists for centuries, was discovered to be due to the presence of nanoparticles in the glass. In particular, to two different metallic nanoparticles: silver nanoparticles (AgNP) and gold nanoparticles (AuNP). Here we show how dichroic silver nanoparticles and gold nanoparticles can be embedded in a 3D printable material in order to reproduce the same dichroic effect of the original Lycurgus cup.

Photopolymerizable, photoisomerizable, photodimerizable and photoluminescent dichroic chromophores are deliberately designed and used for comprehending the sequential realization of the polyimide-free in situ photoalignment of liquid crystals (LCs). Upon a linearly polarized UV-light (LPUV) treatment, the multifunctional photoaligning additive, homogeneously dissolved in a LC mixture, is interfacially polymerized at the inner surfaces as a thin photo-responsive polymer layer. Subsequently, the molecular orientational anisotropy is induced by the dichroic photochromic responses, resulting in a uniaxial planar LC alignment. The reversible trans/cis-isomerization plays a crucial role for the LC alignment, rather than irreversible [2+2] dimerization. Therefore, the LC aligning effect is strongly influenced by the wavelengths of LPUV. Under the longer wavelength UV-irradiation (λ > 350 nm), the reversible isomerization is more preferable to the irreversible dimerization, resulting in a rewritable LC alignment with much better alignment quality. Such sequential processes are evidenced by monitoring spatial and orientational distributions of the self-labeled dichroic fluorescent monomers during the process. The conclusions are further corroborated by the wavelength dependencies of the photochromic responses, LC aligning effect, and rewritable LC alignment.

An Inductive Frequency Selective Surface (IFSS) self-standing dichroic sub-reflector is presented, which allows the transmission of two frequency bands and reflection of a third band. The operating frequency of the sub-reflector is designed to work at Ku, K and Ka frequency bands, intended for earth to space and space to earth satellite communications. The proposed unit cell is a Jerusalem cross intertwined with an Brigid's cross. The IFSS is investigated using transmission line theory, along with equivalent-circuit model technique. It has been designed, and simulated using CST Microwave Studio and Advance Design Simulator (ADS). The cascade configuration of the IFSS is also investigated to improve frequency roll-off and bandwidth of the reflection and transmission coefficients. The IFSS has been manufactured using two-sided Photo Chemical Machining (PCM) technique, and has been experimentally characterized using an optical configuration, comprising two double ridged horn antennas connected to a VNA and a rotation system. Measured results are in good agreement with theoretical and simulation data, which validates the reliability of the design and manufacturing process.

A BODIPY dye functionalized with uracil-ethynyl groups at the 2,6-positions supramolecularly polymerized into J-aggregates directed by intermolecular H-bonds and featured intense absorption and resonant fluorescence. The alignment of J-aggregated chromophores in a thin film was achieved by a rubbing method and polarized photoluminescence with a dichroic ratio up to 14.3 was obtained.

We report a robust method of stabilizing a laser to the frequency of an atomic transition using a hollow cathode lamp. In contrast to the standard dichroic atomic vapor laser lock method, which uses dichroism induced by a longitudinal magnetic field, we employ birefringence induced by a transversal magnetic field. We applied this method to the ( 5 s 2 ) 1 S 0 − ( 5 s 5 p ) 1 P 1 transition (461 nm) of Sr. Although the hollow cathode is made of ferromagnetic material, we successfully applied a magnetic field of sufficient strength to obtain an error signal with a theoretical maximum slope. This method may be applied to other hollow cathode lamps of different atomic species.

The in-flow detection of microparticles is of great importance in biomedical fields. Previous studies have shown that twodimensional (2D) light scattering technology has the capability to detect and differentiate unlabeled cells, while fluorescence imaging can be used as a specific cytological detection method. Here, we built a system to acquire simultaneously the 2D light scattering patterns and fluorescence images of single microparticles in flow. A 488 nm laser beam was reshaped into a light sheet by a cylindrical lens, which was used to excite the microparticles in a microfluidic tube. The 2D light scattering and fluorescence signals were collected by a 10x objective lens through a 505 nm dichroic beam splitter, and they were simultaneously acquired by dual complementary metal oxide semiconductor (CMOS) detectors. Our system acquired the 2D light scattering patterns and fluorescence images of single microparticles from a mixture (2 μm fluorescent particles, 2 μm and 3.87 μm non-fluorescent particles) in flow. Based on the 2D light scattering patterns and the fluorescence images, the number and the ratio of mixed microparticles can be determined. Moreover, the label-free microparticle size differentiation can also be achieved with the 2D light scattering patterns. The detection of microparticles in flow that combines label-free 2D light scattering technology and fluorescence imaging may find potential applications for single cell analysis.

Two-dimensional (2D) materials have been attracted highly interest in recent years due to their low structural symmetry, excellent photoresponse and high air stability. However, most 2D materials can only response to specific light, which limits the development of wide spectrum photodetectors. Proper band gap and the regulation of Fermi level are foundations for realizing electronic multi-channel transitions, which is an effective method to achieve wide spectral response. Herein, a noble 2D material, Palladium phosphide sulfide (PdPS), is designed and synthesized. The band gap of PdPS is around 2.1 eV and the formation of S vacancies, interstitial Pd and P atoms promote the Fermi level very close to the conduction band. Therefore, PdPS-based photodetector shows impressive wide spectral response from solar blind ultraviolet (SBUV) to near infrared (NIR) based on the multi-channel tranisiton. It also exhibits superior optoelectrical properties with photoresponsivity (R) of 1×103 A/W and detectivity (D*) of 4×1011 Jones at 532 nm. Moreover, PdPS exhibits good performance of polarization detection with dichroic ratio of ∼3.7 at 808 nm. Significantly, it achieves polarimetric imaging and hidden target detection in complex environments through active detection. This article is protected by copyright. All rights reserved.

Linear dichroic anisotropic photonic materials are highly attractive due to their great potentials in many applications, which in combination with the ferroelectric properties could broaden their research and applications. However, to date, the linear dichroism conversion phenomenon has not been observed in one-dimensional (1D) large-size single-crystal materials: in particular, lead-free perovskite ferroelectric crystals. Here, we propose a new ferroelectric design strategy: namely, partial organic cation substitution for precisely designing 1D polarization-sensitive perovskite ferroelectrics. As an example, the 1D mixed-cation perovskite ferroelectric (n-propylammonium)(methylammonium)SbBr5 was synthesized, which exhibits a fascinating ferroelectricity with a notable reversible polarization of 2.9 μC/cm2 and a large ferroelectricity-driven polarization ratio of 6.9. Importantly, the single-crystalline photodetectors also exhibit superior optoelectronic anisotropic performances at the paraelectric phase, having a large photoelectric anisotropy ratio (∼35), an excellent polarization-sensitive dichroism ratio (∼1.31), highly sensitive detectivity up to ∼109 Jones, and a fast response rate (∼45/68 μs). This finding provides a significant and effective pathway for the targeted design of new functional lead-free linear dichroic anisotropic photonic ferroelectrics.

Enantiopure helicene-porphyrin conjugates were prepared. They show strong changes in their circular dichroic response as compared to classical helicene derivatives, with highly intense bisignate Exciton Coupling (EC) signal and De values up to 680 M-1 cm-1 for the Soret band. They also display circularly polarized fluorescence in the (far-)red region, with dissymmetry factors up to 7 x10-4.

TiN and ZrN are emerging as important alternative plasmonic materials. In addition to their well-known assets, they can incorporate point defects that break the centrosymmetry of their cubic crystal structure, making them promising candidates as nonlinear optical materials, especially for second-harmonic generation (SHG). Their refractory character and chemical stability have been obstacles for the bottom-up fabrication of TiN and ZrN nanostructures so far. In this work, it is shown that highly directional dichroic nanostructures of TiN and ZrN may be indeed grown by self-assembly using glancing angle deposition on periodic rippled dielectric surfaces. The produced nitride nanostructures exhibit point defects and exceptional photothermal durability. These nanostructures exhibit strong SHG response when probed by a near-infrared laser. It is shown that SHG is strongly associated with the near-field enhancement due to localized surface plasmon resonance of the nanostructures. Given that such nanostructures can endure extremely high electric fields, they are expected to be able to emit massive SHG signals and be applied in laser technology as optical components such as polarizers and SHG emitters.

A method to drastically enhance detection efficiency of a linear variable filter (LVF) sensor across an extended and continuous wavelength range is presented. The efficiency is increased by a wavelength preselection concept, where the incoming light is divided into partial spectra to reduce otherwise unavoidable reflection losses of filter-based spectrometers. The simple but effective setup uses selected and successively arranged dichroic beamsplitters, which ensures an optimized compromise between efficiency enhancement and minimum increasing complexity. When connected to a two-dimensional camera and combined with a tilted LVF, this compact optical system allows the continuous recording of the full wavelength range between 450 and 850 nm with a resolution of ∼19 nm at 508.6 nm. An efficiency enhancement factor of up to 5.7 is achieved in comparison to a conventional LVF setup. The working principle was verified by measuring the reflection spectra of different natural and artificial green leaves. The proposed approach for increasing the efficiency can be miniaturized and applied to a broad range of other filter-based sensors.

This contribution describes an approach to realize dichroic mirrors for fifth-harmonic separation with a diameter of 12”. The optics will be used at the National Ignition Facility to build a diagnostic based on Optical Thomson Scattering, which requires a high energy, pulsed laser operating at 211nm wavelength. Since the ultra-violet absorption edge of the most commonly used high refractive coating materials is above 211nm, only a few oxide materials as for example alumina are suitable for this wavelength. The applied material combination Al2O3/SiO2 provides a small refractive index contrast of about 0.2, which requires a coating process with a very high precision and uniformity to realize complex thin film designs. To achieve a physical layer thickness uniformity better than 0.5%, the linear motion concept of the MAXIMA ion beam sputtering machine [1] is combined with an additional substrate rotation. The layer thickness is controlled precisely by optical broad band monitoring in the wavelength range from 220nm to 1050nm. To realize a surface figure of λ/10 at 633nm for a clear aperture of 250mm diameter, the multi-antireflection coating on the backside is utilized for stress compensation. Experimental results regarding the spectral performance, the mechanical stress, the surface roughness and the laser damage resistance will be presented and discussed.

Here we present soft X-ray linear dichroic ptychography developed at the COherent Scattering and MICroscopy (COSMIC) beamline at the Advanced Light Source (ALS) by studying biominerals—complex 3D hierarchically structured mineral-organic composite materials—produced by living organisms. Sequences of soft x-ray ptychography images at varying EPU polarizations were acquired, which principally allows visualization and orientation mapping of complex biogenic ultrastructures with spatial resolution down to 8 nm. These correlative data not only shed light on key mechanisms of the formation and mechanical principles of these composites but also demonstrate the capabilities and limitations of this newly developed technique, such as orientational precision, angular resolution and thickness related restrictions.

Layer-by-layer fabrication of uniformly oriented thin films over large areas by cost-effective solution-based approaches can open new horizons for the realization of high-performance organic circuits in various applications. In this work, fabrication of a large-area ≈40 cm2 film with uniform orientation is reported for poly(3,3‴-dialkylquaterthiophene) (PQT) using a unidirectional floating film transfer method (UFTM). Orientation characteristics and charge transport anisotropy were analyzed using polarized UV-vis spectral mapping and fabrication of bottom-gated organic field-effect transistors (OFETs) from different regions. Films were found to be highly oriented with an optical dichroic ratio of ca. 15. Orientation characteristics reveal that films were highly oriented along the width of the film, covering >70% of the area, and angle-dependent field-effect mobilities are in good agreement with the orientation of the polymer backbones. These highly oriented films resulted in charge transport anisotropy of 8.9. An array of bottom-gated OFETs fabricated along the length of single large-area (≈15 × 2.5 cm2) thin film demonstrated the average field-effect mobility of 0.0262 cm2/(V s) with a very narrow standard deviation of 12.6%. We also demonstrated that film thickness can be easily tuned from 5.6 to 45 nm by increasing the PQT concentration, and field-effect mobility is highly reproducible even when the film thickness is 10 nm. Microstructural characterization of the thus-prepared large-area thin films revealed the edge-on stacked polymer backbones and surface roughness of

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.

Recently, the field of laser radiation detection LRD has witnessed a great development in the past three decades; there has been a great development in the field of semiconducting devices and optical systems to achieve high-performance LRD. Many important applications mainly depend on LRD in Civilian and military fields, like LIDAR systems, remote sensing, optical fiber communication system, and in military application laser-guided bomb LGB and laser warning receiver LWS. In all these applications, the laser sensors are chosen according to the requirements of the application in terms of sensitivity, a field of view, and the speed of the sensor's response in terms of converting the optical signal into electrical. In this paper, three-channel dichroic beam splitters, sky cameras, and a main optical system are utilized to identify the wavelengths of the incident laser radiation in the far-field. The optical system is designed to give a high-quality monochromatic image of LIDAR receivers and neglect a background noise from sunlight. The main contribution of This optical system is to reduce the electronic components and increase the optical components to enhancement the signal-to-noise ratio to achieve more than 50 dB in clear weather conditions of a LIDAR receiver by using the dichroic beam splitter technique with a sky cameras detector.

In multiphoton ionization of atoms, elliptical dichroism may arise in the photoelectron angular distributions due to the interference of the possible ionization pathways. We here consider the interaction of atoms with an elliptically polarized biharmonic ($\ensuremath{\omega} + 2\ensuremath{\omega}$) field which simultaneously allows one- and two-photon ionization of the atoms. The interference between these two ionization pathways introduces contributions to the elliptical dichroism in addition to the dichroism that arises from the two-photon ionization alone. We show that these additional dichroism contributions can lead to a stronger dichroism in comparison to the one arising from two-photon ionization only. We present a relativistic analysis of the corresponding photoelectron angular distributions and discuss individual contributions to the dichroic phenomena. Detailed computations have been performed for biharmonic ionization of neutral helium atoms.

Among large numbers of transition metal dichalcogenides (TMDCs), monolayer rhenium disulfide (ReS2) is of particular interest due to its unique structural anisotropy, which opens up unprecedented opportunities in dichroic atomical electronics. Understanding the domain structure and controlling the anisotropic evolution of ReS2 during the growth is considered critical for increasing the domain size toward a large-scale growth of monolayer ReS2. Herein, by employing angle-resolved Raman spectroscopy, we reveal that the hexagonal ReS2 domain is constructed by six well-defined subdomains with each b-axis parallel to the diagonal of the hexagon. By further combining the first-principles calculations and the transmission electron microscopy (TEM) characterization, a dislocation-involved anisotropic evolution is proposed to explain the formation of the domain structures and understand the limitation of the domain size. Based on these findings, growth rates of different crystal planes are well controlled to enlarge the domain size, and moreover, single-crystal domains with a triangle shape are obtained. With the improved domain size, large-scale uniform, strictly monolayer ReS2 films are grown further. Scalable field-effect transistor (FET) arrays are constructed, which show good electrical performances comparable or even superior to that of the single domains reported at room temperature. This work not only sheds light on comprehending the novel growth mechanism of ReS2 but also offers a robust and controllable strategy for the synthesis of large-area and high-quality two-dimensional materials with low structural symmetry.