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In order to achieve both adjustable wideband and high Polarization Conversion Rate (PCR) of the transmitted waves, a novelty tri-layered structure is proposed for terahertz applications. The Rhombus Hollow Square (RHS) is built up by top and bottom gold gratings on Silicon Dioxide and Polyamide substrate with graphene strips. The proposed polarizer broadens the bandwidth and has well performance. As chemical potential increases, the bandwidth is also broadened by adjusting the graphene. From 0.5 THz to 3 THz, the PCR is greater than 90%, and the relative bandwidth up to 142.9%. The transmission and absorption of polarizer are analyzed at the oblique incidence with chemical potential 0.1eV. By simulating and analyzing the performance, a new result of maintaining broadband and high transmittance in oblique incidence is obtained.

A novel millimeter-wave (mm-wave) wideband circularly polarized (CP) horn antenna using iris polarizer is reported. By introducing the metasurface concept, the electrical contact problem at the mm-wave band for waveguide-separated components of high-performance CP horn antenna is eliminated. The influence of air gaps on polarizer and whole horn antenna loaded and unloaded metasurface is analyzed and explained. According to simulation, small air gaps of the metal-to-metal contacting plane would not harm the horn performance after loading the metasurface, which means the proposed method can achieve a better tolerance of manufacturing and assembly errors and is more suitable for high-frequency CP horn design. For validation, the proposed horn antenna has been fabricated and its performance is evaluated. The measurement results are in good agreement with the simulation results. The experimental results of 37.8% bandwidth from 75 to 110 GHz for both the axial ratio (AR) $\vert S_{11}\vert dB are achieved.

In this article, a new concept to improve the angular stability of linear-to-circular polarizing reflectors is presented. It is first explicitly demonstrated that existing design approaches heavily rely on the adjustment of the design stack-up, namely, the substrate height and relative permittivity, to the desired operating frequency. An approach is then proposed for decoupling the performance from the substrate parameters. The proposed approach provides increased design flexibility, resulting in performance improvement. Insight on the operating principle is provided resorting to equivalent circuit models. Subsequently, the benefits of the angularly stable reflection polarizer are demonstrated by a practical example involving a multiple beam antenna implemented using materials and processes compatible with satellite missions. The antenna exploits an innovative quasi-optical beamformer as primary feed combined with a cylindrical polarizing reflector. Numerical and experimental results from this antenna architecture are presented to confirm the improvements achieved with the proposed concept over existing designs. The close comparison of simulations with measurements that are achieved validates the concept and the design approach.

Thermal treatment has been proved as an efficient and promising method for LCD panel scraps pre-treatment and resource recycling. However, undesirable pollutants including polycyclic aromatic hydrocarbons (PAHs) and heavy metals tend to occur during the thermal treatment. To better understand the metals migration behavior and to illustrate the interaction effect between organics and metals, effect of the polarizer on the metals (Cr, In, Ni, Cu, Zn, Fe) migration and transformation behaviors was analyzed in this study. Results showed that polarizer, the main organic component in LCD panel, could enhance the metals migration behavior during the thermal treatment and also affect the metals speciation distribution in solid residue. The enhancement effect on metals migration rate was mainly deduced by the gas/volatile compounds from polarizer decomposition, while the metals speciation distribution in solid residue was mainly affected by the solid product from polarizer decomposition. The polarizer also showed increase effect on the potential risk of In, Cu and decrease effect on Fe in solid residue. The results suggest that reducing the organics content or adding solid carbon in treatment system would helpful to decrease the metals migration during thermal treatment process of discarded LCD panels.

The reversible insulating-to-conducting phase transition (ICPT) of vanadium dioxide (VO2) makes it a versatile candidate for the implementation of integrated optical devices. In this paper, a bi-functional in-line optical device based on a four-layer stack of PMMA/graphene/VO2/graphene deposited on a side-polished fiber (SPF) is proposed. The structure can be employed as an ultra-compact TE modulator or a TM-pass polarizer, operating at 1.55 μm. We show that the ICPT characteristic can be used for polarization-selective mode shaping (PSMS) to manipulate orthogonal modes separately. On the one hand, as an optical modulator, the PSMS is used to modify mode profiles so that the TE mode attenuation is maximized in the off-state (and IL is minimized in the on-state), while the power carried by the TM mode remains unchanged. As a result, a TE modulator with an ultrahigh extinction ratio (ER) of about ER = 165 dB/mm and a very low insertion loss (IL) of IL = 2.3 dB/mm is achieved. On the other hand, the structure can act as a TM-pass polarizer featuring an extremely high polarization extinction ratio (PER) of about PER = 164 dB/mm and a low TM insertion of IL = 3.86 dB/mm. The three-dimensional heat transfer calculation for the ICPT process reveals that the response time of the modulator is in the order of few nanoseconds. Moreover, the required bias voltage of the proposed device is calculated to be as low as 1.1 V. The presented results are promising a key step towards the realization of an integrated high-performance in-line modulator/polarizer.

Using polymerizable cholesteric liquid crystal (CLC) paints, we prepare circularly polarized freestanding films that enable students to acquire a basic understanding of circular polarization and molecular chirality. The polymerized helical structures of CLC films can exhibit brilliant structural colors by selective reflection of visible light corresponding to their helical pitch. For the fabrication of freestanding and circularly polarizing films of various colors and shapes, students control helical pitch with the amount of chiral dopants and stabilize them by photopolymerization. On the basis of an understanding of the circularly polarized reflection of CLC paints, students can encode secret letters that are visible only with a specific circular polarizer.

The problems of polarizer`s construction over the basis of the circular waveguide for a work in Ka – range are highlighted in the article. The purpose of the article is to establish the possibility of using the proposed design for the construction of high-tech Ka-band polarizers and to prove the correctness of analytical expressions for determining the structural dimensions by experimentally obtained characteristics. The analysis of the current decisions from the point of view of construction and technology is held. On the conclusion had been drawn more technological polarizer`s construction with the calculation of the main constructive sizes is proposed. Theoretical principles of construction and calculation of structural dimensions of the C and Ku ranges polarizers’ phase-shifting sections are covered in detail in the works of modern researchers and tested on real devices . However, while constructing AFT elements designed to operate in higher frequency operating bands, such as the Ka – band (20/30 GHz), there are certain difficulties, the solution of which continues. In order to check the proposed decision experimental model of polarizer was made and investigation of the main characteristics corroborating the right theoretical assumption was held. For a practical study of the proposed design, a mock-up of a polarizer based on a round waveguide with an inner diameter of 11 millimeters was made. In the prototype, the rod structure was implemented in the form of five pairs of adjusting screws with a diameter of one millimeter. The final length of the polarizing plate, taking into account the smooth transitions designed to align the plate with the waveguide, was defined as the sum of the lengths of its regular part and one smooth transition multiplied by 0.9. The experimentally obtained characteristics confirm the possibility of using the proposed design for the construction of high-tech Ka-band polarizers, and the correctness of analytical expressions for the determining the structural dimensions. A further development of the proposed solution may be the analysis and finding the necessary analytical relationships between the structural dimensions of the rod and dielectric structures in order to expand the operating range of the polarizer.

We propose and demonstrate a fabrication-friendly on-chip polarizer based on polarization-selective corner mirrors. The total internal reflection angles are distinct between TE and TM modes due to the strong birefringence of silicon-on-insulator (SOI) waveguide. Thus, by properly choosing the inclination angle, TE mode can be completely reflected at each corner mirror with negligible losses, whereas TM mode can be efficiently filtered out. The minimum feature size of such polarizer is as large as 400 nm. The measurement results show low excess losses of 20 dB over a 200-nm bandwidth. Such high performance can be maintained even with a large width deviation of $> \pm 50$ nm.

'Smart' windows which reversibly increase their reflectivity upon heating are attracting considerable attention as devices for maintaining comfortable indoor environmental conditions. In this work, twisted nematic semi‐interpenetrating liquid crystal networks which lose their order upon heating are sandwiched between reflective linear polarizers. This 'smart' window reversibly decreases its transmission from about 50–10% over a wavelength range between 400 and 1100 nm upon heating, resulting in the window becoming darker and reflecting more light. This 'smart' window is potentially interesting for energy saving window applications where variation between privacy and visible light transparency states is required.

A millimeter-wave (mm-Wave) wideband dual circularly polarized (CP) antipodal septum antenna is proposed. By introducing two antipodal septum blames in widened rectangular waveguide and the corresponding feeding network, the operating bandwidth of the septum antenna is enhanced. The working principle of the generation process of dual CP is explained by a three-port model with three excitation conditions. In addition, the asymmetrical radiation pattern of the classical polarizer consisting of square waveguide and single septum caused by the high-order modes is explained and eliminated. To verify the design, the proposed antenna has been fabricated and measured. An operating bandwidth of 37.4% for reflection coefficients less than −13.8 dB, isolation better than 22 dB, and axial ratio (AR) value less than 3 dB is achieved.

In this paper, an ultra-wideband (UWB) polarizer with high performance based on the metasurface is designed and demonstrated, which is composed of a dielectric substrate with a double-gap circular pattern and metal film. Multiple strong resonance points enable the design to achieve the conversion from incident linearly polarized waves to cross-polarized waves at 6.49–11.64 GHz, with a fractional bandwidth of 56.8% and a corresponding polarization conversion rate (PCR) of 90%. The PCR remains above 90% at 6.49–11.52 GHz when the electromagnetic wave is obliquely incident between 0° and 30°. Furthermore, the surface current distribution of the polarizer is discussed to explain the physical mechanism. The sample is fabricated for microwave validation. Compared with previous reports, the proposed polarizer has a larger bandwidth and higher efficiency and is expected to be used in microwave communications, antennas, radar cross section reduction, and other fields.

For flexible displays, there is a desperate need for a broadband coatable polarizer that can absorb light in a specific direction. Conventional polarizers fabricated by the polymer stretching process are too thick (50-200 μm) to be used as polarizers that can be applied to antireflective films in flexible displays. For the development of the broadband coatable thin film polarizer, diacetylene (DA) amphiphiles containing I- or I3- are newly designed and synthesized, and the content of DA amphiphiles in the 4,6-decadiyne solvent is optimized to form a lyotropic liquid crystal (LLC) phase. Topochemical polymerization of uniaxially oriented iodine-based DA not only stabilizes the film but also broadens the polarization light region from 350 to 700 nm. The transfer and amplification of iodine and DA functions in uniaxially oriented thin films enable the fabrication of broadband coatable thin film polarizers.

In this letter, a broadband 1 bit reconfigurable transmitarray antenna (RTA) based on polarization rotation element is proposed. The transmitarray element is composed of two split circular rings connected by two narrow strips and sandwiched by two orthogonal polarizers. As phase shift and polarization conversion structure, the two patches are separated by the air layer, and the p-i-n diodes are soldered in the center of the narrow strips. The polarizer grids are used as dc bias lines to conduct p-i-n diodes. By controlling the p-i-n diodes in the on and off states, the polarization orientation of the wave emitted by the RTA element is changed. Then, the outgoing waves in the two states physically form a broadband 180° phase difference, which broadens the operating bandwidth of the RTA effectively. By utilizing the novel unit cell, a 16 × 16 elements RTA is designed, fabricated, and measured. The measured results show that the 3 dB and 1 dB gain bandwidths are 45% and 17%, respectively. The peak gain is 16.8 dBi with aperture efficiency of 18.4%. Furthermore, the proposed RTA has good beam scanning performance with 2-D scanning range of ±40°.

The design of an automated laboratory goniophotometer CHERRY (CHlorophyll Estimation and Reflectance Registration sYstem) intended for measuring the spectral reflectance coefficients [SRC(λ)] of conifer needles in the range 400–2500 nm and quantitatively analyzing the content of colored pigments in needles in the range 400–700 nm is described. The CHERRY goniophotometer allows two types of measurements to be made: goniometric ones in which the spectral reflectance is measured from the test sample in the vertical direction and photometric ones in which the transmittance of direct radiation passed through a cuvette with a pigment solution is measured. Spectral reflectance measurements of spruce needles (Picea abies) in the range 400–700 nm showed differences up to 15% by employing extended or quasi-parallel sources. Vegetation index Vog2 for healthy needles varied from –0.45 to –0.34 for different sample positions and from –0.42 to –0.39 for different orientations of the polarizer for a selected sample position. The relative deviation of the measured spectral reflectance in the range 470–770 nm of up to 5% for 2-hour measurements confirms that the lab radiation source influences the spectral reflectance of the needles. Quantitative measurements show that healthy needles contain 30% more of the studied pigments than needles from a tree in a state of stress.

On the basis of rigorous dynamical-theory calculations, a complete X-ray polarization-switch effect of silicon crystals at the exact multiple-beam diffraction condition is demonstrated. The underlying physical mechanism of this unique phenomenon can be revealed using a simple multiple-wave propagation and interference model. The constructive and destructive interference of the multiple detoured-diffraction beams along the direction of the primary diffracted beam directly leads to the complete polarization switch. This phenomenon can be realized using both synchrotron and laboratory X-ray sources at many discrete wavelengths, and used to design a novel crystal-based polarizer to achieve a 90° polarization rotation.

A wideband circularly polarized (CP) array antenna has significant importance in modern communication system. In this paper, we proposed a wide band CP array by combing dual split ring resonators (DSRRs) to dual layer microstrip antenna. A 2 × 2 dual-layer microstrip antenna array is used to radiate wide band linearly polarized wave, and the 3 × 3 four-layer DSRRs is used as an external polarizer which converts linearly polarized wave to circularly polarized wave at distinct frequencies. The proposed array achieves an impedance bandwidth of 20% ranging from 4.57–5.57 GHz and AR bandwidth of 16.83% ranging from 4.57–5.41 GHz. The prominent futures of the proposed array are wide impedance bandwidth on desired frequencies. This new concept is theoretically and experimentally investigated to evaluate the performance of the proposed array, which allows a better prospect for the application of radar and satellite communication systems.

A wideband circularly polarized (CP) pyramidal horn antenna (PHA) is proposed. A +45° or −45° rotated spoof surface plasmon polariton (SSPP) waveguide, which serves as a circular polarizer, is inserted into the PHA. The vertically polarized wave in the PHA is decomposed into two orthogonal components with equal amplitude. One component perpendicular to the circular polarizer propagates along the PHA as a fast wave, and the other one propagates along the SSPP waveguide as a slow wave. When length of the SSPP waveguide is chosen appropriately, the phase difference between these two components is +90° or −90°, which makes the PHA radiate left-handed or right-handed (LH or RH) waves. Furthermore, the phase differences approximately equal to +90° or −90° over a wide frequency range. As a result, a wideband LH or RH CP PHA is implemented. Since the SSPP waveguide is completely inserted into a standard gain PHA, its volume does not increase at all, and its appearance does not change. Measured results show that the CP PHA achieves 26% 3 dB axial ratio (AR) bandwidth (from 8.7 to 11.3 GHz), its reflection coefficients are less than −10 dB, and its gains range from 14.9 to 16.6 dBic.

This letter presents a broadband 3-D-printed circularly polarized (CP) spherical Luneburg lens (LL) with the linearly polarized feed antenna for the X -band. In order to implement spatially continuous varying effective refractive index (RI), the proposed LL is divided to many unit cells and their effective RI is simulated and calculated by effective medium theory. Since the effective RI of unit cells is anisotropic for two orthogonal linearly polarized (LP) waves, the proposed LL is an LP to CP polarizer realized by properly selecting the radius of the LL. The whole structure is fabricated by low cost 3-D-printing (3DP) technic, which is fed by an LP antenna source rotated to a certain angle with respect to the LL around the normal. The measured results indicate that the voltage standing wave ratio (VSWR), axial ratio, and gain enhancement are lower than 2, less than 2.8 dB, and more than 10 dB at X -band, respectively. The results of measurement agree well with the simulation.

This paper proposes an approximate analytical and numerical constructive synthesis method of optimal waveguide polarizers based on three irises in square waveguide. A mathematical model of polarizer has been developed on the basis of waveguide transmission and scattering matrices. The analytical expressions derived for elements of the scattering matrix were used for determining the electrical characteristics of polarizer. The synthesis conditions were developed in the form of a system of equations, the solution of which should ensure the minimal deviation of the differential phase shift with respect to 90°, the maximum possible flat phase frequency characteristic, and the best matching in the specified frequency band. The method was evaluated on the constructive synthesis of polarizers for three working frequency bands: 7.25–8.6, 7.75–8.5, and 8.0–8.5 GHz. The validity of constructive synthesis results was confirmed by the calculation data of characteristics of synthesized polarizers using the finite element method in frequency domain employing the CST Microwave Studio Software. A satisfactory matching of electrical characteristics calculated by both methods was achieved. For the working frequency band of up to 10%, the proposed method of constructive synthesis ensures a sufficient for practical purposes accuracy in determining the dimensions of polarizer and the corresponding electrical specifications. This method can be also recommended for rapid determination of initial values of polarizer dimensions guaranteeing the operation in the vicinity of global optimum and thereby speeding up the designing of optimal polarizers at the electrodynamic level. In addition, this method can be extended to the constructive synthesis of waveguide polarizers with a large number of irises.

The effect of the optical feedback on the polarization flipping point and hysteresis loop was studied. The polarization flipping occurred at all angles between the polarizer axis and the laser polarization. The polarization flipping point changed by an optical feedback occurred at angles from 0° to 90°. Ability of choosing or controlling the laser polarization was determined by changing the direction of vertical and horizontal polarization by polarizer rotation in the external cavity from 0° to 90°.

Metals were for decades perceived as devoid of interesting optical properties that could be harnessed for optical components and devices. However, with the development of accurate nanofabrication techniques and precise control over architectural parameters, metals can be structured and characterized on the nanoscale. Metallic plasmonic nanomaterials exhibit a number of unique structural and optical properties, which offer the potential for developing new types of plasmonic devices. Here, we demonstrate a low-loss broadband polarizer based on a hybrid plasmonic fiber structure using metals as polarization-selective absorption materials. The polarization mechanism, design, fabrication, and characteristics of the plasmonic polarizers are investigated theoretically, numerically, and experimentally. The theoretical analysis predicts that the polarization-selective absorption with insensitivity to wavelength enables hybrid plasmonic fibers to function as broadband polarizers. Numerical simulations give the comparison of the polarization-selective absorption of various metallic nanomaterials (Ag, Au, In, Al, Cr) and show that aluminum is regarded as the optimum absorption material for the plasmonic polarizer. Experimental results show that through precise control over geometrical parameters, this device is capable of offering a high polarization extinction ratio (PER) of over 40 dB and a low insertion loss (IL) of less than 1.3 dB in the wavelength region of 810.1-870.0 nm. Compared with commercial birefringent-crystal-fiber polarizers, the plasmonic fiber polarizer has a better PER and IL bandwidth. These merits, combined with a compact and robust configuration, enable the plasmonic polarizer to have great potential in a broad range of applications.

We propose and numerically investigate the use of birefringent vertical-cavity surface-emitting lasers (VCSELs) under the injection and modulation of spin polarized electrons for application to analog radio over fiber (RoF) systems. Injection current and electron spin polarization in a birefringent VCSEL are individually modulated for generating data signals and a millimeter-wave carrier and a polarizer is used to combine two orthogonal polarizations. A preliminary experiment without spin injections confirms that 24-GHz carrier generation originating from polarization-mode splitting of the birefringent VCSEL can be used for the heterodyne detection of square-wave signals with a period of 6.4 ns. Our findings mark the first step in applying spin-injected birefringent VCSELs having the capability of ultra-high-frequency modulation for application to analog RoF systems.

The dielectric permittivity of a material encapsulates the essential physics of light-matter interaction into the material’s local response to optical excitation. Photo-induced modulation of the permittivity can enable an unprecedented level of control over the phase, amplitude, and polarization of light. Therefore, the detailed dynamic characterization of technology-relevant materials with substantially tunable optical properties and fast response times is a crucial step to realize tunable optical devices. This work reports on the extraordinarily large permittivity changes in zinc oxide thin films (up to −3.6 relative change in the real part of the dielectric permittivity at 1600 nm wavelength) induced by optically generated free carriers. We demonstrate broadband reflectance modulation up to 70% in metal-backed oxide mirrors at the telecommunication wavelengths, with picosecond-scale relaxation times. The epsilon near zero points of the films can be dynamically shifted from 8.5 µm to 1.6 µm by controlling the pump fluence. The modulation can be selectively enhanced at specific wavelengths employing metal-backed zinc oxide disks while maintaining picosecond-scale switching times. This work provides insights into the free-carrier assisted permittivity modulation in zinc oxide and could enable the realization of novel dynamic devices for beam-steering, polarizers, and spatial light modulators.

We investigated the conditions for forming the single-frequency monopulse operation mode of the transversally diode pumped Yb,Er-phosphate glass laser with a passive Q-switch based on the Co2+:MgAl2O4 crystal. It was shown experimentally that the spectral selectivity that ensures the stable single-frequency operation for the Yb,Er-laser is achieved in the intracavity Fabry–Perot interferometer in the form of the totally reflecting mirror and nearest end surface of an active element with plane-parallel faces, as well as the polarization interference filter (PIF, Lyot filter). Meanwhile, the PIF created by an active element with thermally induced anisotropy and a polarizer in the form of a passive Q-switch plate, oriented at Brewster’s angle to the resonator axis, acts as a preliminary spectral selector. The maximum energy of the formed output laser pulses was 6 mJ with a duration of 20.2 ns, a repetition rate of 1 Hz, and a single-frequency lasing spectrum width of 41 MHz.

Visible Light Positioning (VLP) has attracted much research effort recently. Most existing VLP approaches require special designed light or receiver, collecting light information or strict user operation (e.g., horizontally holding the mobile phone). This incurs a high deployment, maintenance and usage cost. We present RainbowLight, a low-cost ambient light 3D localization approach that is easy to deploy in today's buildings. Our key finding is that light through a chip of polarizer and birefringence material produces specific interference and light spectrum at different directions to the chip. We derive a model to characterize the relation for direction, light interference, and spectrum. Exploiting the model, RainbowLight calculates the direction to a chip after taking a photo containing the chip. With multiple chips, RainbowLight designs a direction intersection based method to derive the location. We implement RainbowLight and extensively evaluate its performance in various environments. The evaluation results show that RainbowLight achieves an average localization error of 3.3 cm in 2D and 9.6 cm in 3D for light on, and an error of 7.4 cm in 2D and 20.5 cm in 3D for light off scenario in the daytime.

The features of the terahertz substrate-based wire grid polarizer designing are considered in the work. For this purpose, a literature review of different type polarizer constructions comparative characteristics was presented and the advantage of wire grid constructions was described. An overview of the materials used for the manufacture of suitable polarizers for different radiation wavelengths is given. Based on this, a combined numerical-analytical method of terahertz polarizer parametric design was presented in the paper. The method consists of effective anti-reflective characteristics analytical calculation of the polarizer unit cell structure and their further refinement and expansion by numerical finite element simulation of the electromagnetic wave propagation problem within this structure in the frequency domain with specific boundary conditions. This brings the scientific novelty. The anti-reflective characteristics calculations are based on the analytical effective medium theory which enables designing polarizer as a thin dielectric film with minimum reflectance. The finite element model considers a polarizer unit cell as a waveguide with specific periodic and port conditions. The combination of both approaches brings the possibility to design a polarizer grid and substrate sizes which provide minimum reflectance. An example of terahertz substrate-based polarizer parameters and characteristics calculation by the developed combined method was given. The obtained results are consistent within 1 % error with the assumed theoretical calculations that were obtained by other scientific group. This indicates the adequacy and practical value of the proposed method for the design of polarizers with anti-reflective, high-transmittance, low-loss and robust characteristics. In addition, by using a numerical finite element component, the proposed method is quite simple to extend by changing the geometry of the unit cell to study such promising objects as multilayer polarizers or polarizers based on more complex meta- or composite materials.

A broadband and compact TE-pass/TM-stop polarizer is presented based on hybrid plasmonic grating (HPG) on an x-cut Lithium-Niobate-on-isolator (LNOI) platform. By comprehensively analyzing the effects of metal width on mode effective index, mode similarity, and mode conversion, we demonstrate the structure with a narrow metal layer. The simulation results indicate that the polarizer with a compact length of 9 μm achieves an extinction ratio over 20 dB within the wavelength range from 1470 nm to 1700 nm. The insertion loss is below 2.3 dB in C-band. Furthermore, the polarizer exhibits large fabrication tolerance to current fabrication technology.

The division of focal plane (DoFP) imaging polarimeter operates by integrating a focal plane array (FPA) with a micro-polarizer array (MPA). While the instantaneous field of view (IFoV) error is an inherent problem in such imaging sensor, which negatively affects the imaging accuracy. The influence of IFoV error can be effectively mitigated by optimizing the MPA configuration. In this paper, we propose an MPA configuration design scheme with four basic polarization angles 0°, 45°, 90° and 135° for DoFP imaging polarimeter. First, we analyze the frequency spectrum characteristics of MPA-filtered images and polarization frequency structure is proposed to record the frequency components and their positions. Then we analyze the frequency components and the crosstalk between them. Finally, we propose our design method that formulates the MPA design as a multi-objective optimization problem. And we design MPAs with better reconstruction performance of various sizes by optimizing their spectrum distribution. Besides, the reconstruction performance of many existing MPA designs were tested on statistically estimated scenes or a single image. This paper builds a database of 500 groups of infrared images of four polarization angles to test the performance of various MPA designs. Experiment results demonstrate that the proposed MPA designs outperform the state-of-the-art MPA designs in both objective and visual evaluations. Thus, the effectiveness of our proposed design method is further confirmed.

This communication introduces a new structure of polarizer for generating millimeter-wave (MMW) circular polarization (CP) in a Fabry–Perot cavity (FPC) antenna. It is the first of its kind, which integrates a 3D-printed polarizer with an inserted partially reflective surface (PRS), which contributes to a wideband CP operation with high antenna gain. The realization of CP and gain enhancement can be controlled independently by optimizing the structures of the dielectric part and the PRS of the polarizer, respectively. The proposed antenna consists of a feeding source, a substrate-integrated quasi-curve reflector, and the proposed polarizer. The feeding source and the reflector are able to be fabricated by the conventional PCB technology which is low-cost and convenient in circuitry integration. For validation, a prototype of the FPC antenna with the proposed polarizer operating at 60 GHz has been designed, fabricated, and measured. The peak gain of the antenna reaches to 20 dBic. The antenna achieves an impedance bandwidth of 20% from 54.5 to 66.7 GHz for the reflection coefficient of less than −10 dB. The axial ratio (AR) bandwidth is 12.7% from 56.5 to 64 GHz for AR ≤3 dB. The experimental results confirm a good agreement between simulation and measurement.

Single atomically thick graphene, with unique structural flexibility, surface sensitivity, and effective light-mater interaction, has shown exceptional advances in optoelectronics. It opens a door for diverse functionalized photonic devices, ranging from passive polarizers to active lasers and parametric oscillators. Among them, graphene-fiber biochemical sensors combine the merits of both graphene and fiber structures, demonstrating impressively high performances, such as single-molecule detectability and fast responsibility. These graphene-fiber biochemical sensors can offer tools in various applications, such as gas tracing, chemical analysis, and medical testing. In this paper, we review the emerging graphene-fiber biochemical sensors comprehensively, including the sensing principles, device fabrications, systematic implementations, and advanced applications. Finally, we summarize the state-of-the-art graphene-fiber biochemical sensors and put forward our outlooks on the development in the future.

The purpose of the work was the correct experimental discovery of the effect of “weak” gyrotropy of the “non-gyrotropic” transparent crystals. The original experiment was based on the study of the light transmission (T) of the system: Polarizer—wedge-shaped Crystal’s sample—Analyzer (orthogonal to Polarizer). It was shown that: if the optical axis of the crystal is parallel to the rib of the wedge and to the polarization of the linear-polarized incident light, then the transmission T of the system can be not equal to zero (due to existence of nonzero components (G12) of the antisymmetric pseudotensor of gyration {G} described the “weak” gyrotropy). Using the LiNbO3 crystal as an example, such nonzero T was at the first time experimentally discovered. Absolute value of components G12 of the LiNbO3 crystal was first estimated: ([G12] = (1.50 +/- 0.51) 10-6).

3D printing belongs to the emerging technologies of our time. Describing diverse specific techniques, 3D printing enables rapid production of individual objects and creating shapes that would not be produced with other techniques. One of the drawbacks of typical 3D printing processes, however, is the layered structure of the created parts. This is especially problematic in the production of optical elements, which in most cases necessitate highly even surfaces. To meet this challenge, advanced 3D printing techniques as well as other sophisticated solutions can be applied. Here, we give an overview of 3D printed optical elements, such as lenses, mirrors, and waveguides, with a focus on freeform optics and other elements for which 3D printing is especially well suited.

This article introduces an easy and accurate technique for the full characterization of septum polarizers (SPs) in back-to-back configuration through standard amplitude/power measurements at the rectangular waveguide ports. The proposed calibration algorithm, based on the use of two simple waveguide sections, along with the developed mathematical formulation, allows the complete extraction of the relevant SP parameters: return loss, isolation, cross-coupling (XP) or axial ratio (AR), and copolarization losses (CP). The methodology has been successfully validated for two different designs at Ku -band.

Interfaces formed between a lipid decorated liquid crystal (LC) film and an aqueous phase can mimic the bimolecular membrane where interfacially occurring biological phenomena (e.g., lipid–protein interactions, protein adsorption) can be visually monitored by observing the surface-sensitive orientations of LCs. The ordering behavior of LCs at different phospholipid-based LC interfaces (1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) and lysophosphatidic acid (LPA)) were investigated to determine the sensing of an important cytoplasmic protein (juxtamembrane of epidermal growth factor receptor (JM-EGFR)). At both DLPC and LPA decorated interfaces, the LC adopts homeotropic ordering, causing a dark optical appearance under crossed polarizers. Interestingly, upon the introduction of JM-EGFR to these LC-aqueous interfaces, the homeotropic orientation of the LC changed to planar (bright optical appearance), suggesting the potential of the designed system for JM-EGFR sensing. The use of different lipid decorated LC-aqueous interfaces results in the emergence of distinct optical patterns. For example, at a DLPC laden interface, elongated bright domains are observed, whereas a uniform bright texture is observed on an LPA laden interface. The DLPC decorated LC-aqueous interface is found to be highly selective for the sensing of JM-EGFR with a detection limit in the nanomolar concentration region (∼ 50 nM). When compared to spectroscopic and other conventional techniques, the LC-based design is simpler, and it allows the simple and label-free optical sensing of JM-EGFR at fluidic interfaces.

We propose and demonstrate a novel and simple wavelength switchable multi-wavelength erbium-doped fiber (EDF) laser based on polarization-dependent loss (PDL) modulation with cascaded fiber Bragg gratings (FBGs) as the wavelength comb filter. PDL is generated and controlled by different polarization angles between the polarization state of each lasing line and the optical fiber polarizer in the laser cavity. The PDL modulation balances the difference between the total loss and the wavelength-dependent lasing gain. The relations among gain, loss, and laser output power under different PDL conditions are numerically analyzed on the basis of a simplified Giles model in an EDF laser system. Results show that multi-wavelength lasing lines can be built up by properly tuning the PDLs in different wavelengths. The amount of lasing lines can be switched by changing the PDL intensity in a certain wavelength. In an experiment, the PDL in that certain wavelength is modulated by utilizing four polarization controllable elements, each of which includes an FBG and a corresponding polarization controller (PC). One PC is used to control the polarization state of the reflected lasing line on the center wavelength of the FBG. A four-wavelength individually switchable EDF laser system is demonstrated by utilizing this wavelength switchable method, in which the switching operation for the single-, dual-, triple-, and four-wavelength laser output is verified. The experimental results are consistent with the theoretical results. All wavelength switching operations are conveniently controlled by merely adjusting the PCs. This simple structure and flexible wavelength switchable operations show that this multi-wavelength EDF laser has great potential in practical applications.

A new approach to the development of an optoelectronic device for molecular orientation of functional materials is proposed. Results of the development of its main components are presented: a collimator for the light from an LED and a broad band polarizer with a large angular aperture. The problem of the collimation of a strongly diverging beam from an LED is examined. It is shown that the use of a modified conical lens offers promise for solving this problem. A broad-band polarizer with a large angular aperture, which is an important component of the optoelectronic device, is developed and fabricated on the basis of a multilayered structure.

The performance of free-space optical data transmission is severely deteriorated by the fluctuation of optical signal intensity, which is resulted from the bias drift of electro-optical modulation devices. In order to improve the performance of free-space optical communication systems, a bias-drift avoiding, beam steered free-space optical wireless communication system is presented based on polarization modulation for the first time to the best of our knowledge. An in-fiber diffraction device based on a 45° tilted fiber grating (TFG) serves simultaneously as an in-fiber polarizer, free-space light emitter, and beam steerer in the proposed communication system, which endows the proposed system with the merits of highly efficient, compact, stable and bias-drift free. The usage of 45° TFG has three benefits: 1), it realizes polarization modulation preventing bias-drift due to its polarization sensitive feature; 2), it enables stable and highly efficient in-fiber compact free-space light emitter; and 3) it accomplishes free-space beam steering due to its wavelength-depending diffraction characteristic. A 2.1 m free-space optical wireless data transmission has been demonstrated with a data rate of 4.8 Gbps per beam using 1.2 GHz bandwidth OFDM signals. This proposal prevents the bias drift issue and maintains high stability. Hence, it can be applied in some harsh situations and confidential data transmission fields.

Multilayer grid polarizers for millimeter waves produced with photolithographic technology have been simulated. Polarizers have spectral bands of enhanced performance where polarization extinction ratio in decibels grows in proportion to the number of layers. Full-wave modeling is compared with three asymptotic models for subwavelength gratings using adjusted grating parameters. Random variations of interlayer spacings reduce the enhancement of polarizing performance, yet the latter continues to grow in proportion to the number of layers. Broadband signal detection is also considered.

An in-line high efficient polarizer, composed of magnetic-ionic-liquid-adorned (MIL-adorned) hollow-core anti-resonant fiber (HARF), is theoretically proposed and experimentally demonstrated. The protocol is based on the selective conversion of polarization mode into leaky mode and attenuates quickly in MIL and the polarizer is featured by the magnetically tunable polarization extinction ratio (PER) and the thermally controllable operation bandwidth.

Frequency-selective surfaces (FSSs), have various applications in microwave electromagnetics. This paper reports a solution to the current FSS challenges of flexibly, low profile, simple fabrication and polarization control using a novel structure operating across X and Ku frequency bands where a linearly polarized wave is rotated by 90°. The FSSs were fabricated by laser engraving a thin layer of $5\mu \text{m}$ aluminum on a $65~\mu \text{m}$ Mylar substrate with a relative permittivity of 2.7, and separated by a dielectric spacing layer of 0.9 mm polypropylene substrate, with a relative permittivity of 3. The co and cross-polarized reflection and transmission response of the structure was investigated using numerical modeling and was measured experimentally. A parametric study was also conducted focusing on key performance indicators, and specifically the bandwidth of the structure. The novelty of this polarization rotation structure lies in its ultra-thin profile ( $0.034~\lambda _{0}$ ), flexibility and significant transmission bandwidth. The fabricated prototypes experimental results were in good agreement with the simulated results, with a simulated −6 dB bandwidth of 61% and a measured −6dB bandwidth of 60%. Applications include antenna radomes where polarization is particularly important, as well as other polarization filtering applications which require a conformal low profile structure.