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In this paper, a compact and low-profile beam steering circularly polarized folded reflectarray antenna (CPFRA) with low scan loss for wide-angle coverage is proposed and designed. In order to obtain lower scan loss over a wider beam coverage range (BCR), a multibeam optimization method considering the illumination weighting factor is introduced to obtain minimum phase errors for the designed beam direction. To improve antenna compactness and alleviate the mutual couplings among multiple feeding sources, small-size substrate integrated waveguide (SIW) cavity-backed slot antennas are employed as the feeding sources, which are integrated with the single-layer reflector board. An incident angle insensitive circular polarizer is designed and integrated over the antenna aperture to achieve circularly polarized (CP) radiation over a wide BCR. At last, a 15-beam CPFRA working at Ka-band, with size 140 mm × 140 mm is designed, manufactured, and measured to validate the proposed design method. Measurement results show that the designed CPFRA can achieve a rather flat gain, with only a 2.1 dB scan loss, across the wide 3-dB BCR of ±29°. The good CP beams are formed over the entire coverage range without any blind zone. With the advantages of wide-angle coverage, low scan loss, and high integration, the proposed beam steering antenna is promising in applications such as 5G communication, radar imaging, and target recognition.

A wideband omnidirectional circularly polarized (CP) antenna using a conformal artificial anisotropic polarizer is proposed for millimeter-wave applications. The antenna consists of three parts: an omnidirectional linearly polarized (LP) radiator, an annular hyperbolic lens, and a conformal anisotropic polarizer. The annular hyperbolic lens regulates the spherical wavefront from the LP radiator into a cylindrical shape prior to propagating into the conformal artificial anisotropic polarizer. Each curved slab of the polarizer is conformally tilted 45 degrees to the incident electric field. Therefore, the conformal polarizer is the three-dimensionalization of the two-dimensional planar artificial anisotropic polarizer. The polarizer designing methodology is the first of its kind to generate wideband CP wave omnidirectionally. The hyperbolic lens and the conformal polarizer are fabricated together using stereolithography (SLA) 3D printing technology. Measurement results show that the antenna has a wide operating bandwidth of 45% (from 24 to 38 GHz), which completely covers potential 5G 28-GHz spectra. The proposed design has a low fabrication complexity and brings possibilities for high-speed wireless communications utilizing circular polarization.

A novel reflectarray (RA) with ultra-low-profile and 2-bit phase quantization beam-steering ability is presented in this paper. To reduce the profile, a Leaky-wave feed is used to excite the RA with enhanced illumination efficiency. Moreover, simultaneous sum and difference patterns are also obtained to provide beam flexibility. The entire thickness of the proposed RA is less than 3% of that of the conventional front-fed RA with the same aperture. To increase the efficiency of the RA, a novel unit cell consisting of a polarizer layer and a reflection layer is developed, which is configured to provide polarization rotation and 2-bit phase shifts by using a hybrid of tunable polarization and discrete resonator. The operation principle, theoretical explanation, and implementation of the proposed antenna are elaborated in this work. To prove the design concept and beam scanning performance, an array with 9×7 unit cells operating at Ka-band is designed and simulated firstly. 2-D beam scanning within the range of ±30° has been verified. Then, a passive prototype with 9×67 unit cells is designed, fabricated and measured. Experimental results show aperture efficiency of 35.1% and illumination efficiency of 43.4%. The developed RA is scalable, and it provides a viable low-cost solution to develop low-profile, high-gain and beam-steering array antennas for satellite applications.

We present the structural design and polarization-maintaining performance of solid-core anti-resonant fiber with two nested circular tubes in 3 m wavelength for the first time, to the best of our knowledge. Numerical simulation results indicated that laser fundamental mode could be obtained by filling the specially designed fiber model with materials of different refractive indices to form the completely solid configuration. We calculated the bend loss of fiber to demonstrate the preferable birefringence performance and outstanding light-confining ability. With the structural deformations from resonant tubes, the birefringence coefficient was enhanced significantly from 210-5 to 6.9310-5, which was of great importance in the polarization sensitive systems. In particular, when nested circular tubes were moved to introduce deformations, the confined loss difference in two orthogonal polarizations was calculated more than two orders of magnitude, which was the desirable result to promote the fabrication of the linear polarizer in 3 m wavelength.

A broadband low-profile folded transmitarray is proposed and investigated, in which a novel wideband transmission polarizer (TP) is used to realize low-profile design. The proposed TP, mainly consisting of a differential-fed grid-slotted patch antenna, can realize high-efficiency transmission and polarization selection simultaneously within a wideband frequency range. Moreover, the proposed TP can realize linear transmission phase because of the true-time delay (TTD) technique. Owing to the function of polarization selection and linear transmission phase, the TP can be used as antenna element for a folded transmitarray. A 140-element folded transmitarray (FTA) is designed and fabricated by combining the TP with a broadband polarization rotation reflecting surface (PRRS). The measured radiation patterns agree well with the simulated results, and a peak gain of 24 dBi and maximum aperture efficiency of 44.7% are achieved. Furthermore, -1 dB and -3 dB gain bandwidth with 25.9% and 33.3% are also experimentally demonstrated in the proposed FTA, respectively.

A novel electrically reconfigurable circular polarizer with high efficiency is proposed. The combination of a slot and a metal strip inclined at a certain angle could achieve circularly polarized radiation. Therefore, the polarization of the antenna can be controlled by controlling the metal strip. The proposed circular polarizer structure is simple, which is realized by two crossed dipoles printed on the top and bottom of the PCB, respectively. A microstrip coupled slot antenna is used to feed the polarizer. By controlling the PIN diode in the middle of the dipole, switching between two circular polarizations is realized. Based on the proposed antenna element, a 22 antenna array is implemented with a sequentially rotated (SR) feeding network. With the difference in the feeding phase, the radiation beam of the array can be changed while switching the polarization state. Measured results show that the antenna element achieves a peak gain of 6.4 dBic with an overall axial ratio (AR) bandwidth of 2.44-2.5 GHz for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) with radiation efficiency of about -1 dB. The proposed antenna features high efficiency, electronically reconfigurable polarization, and low cost, which is well suited for base station application

This paper describes the noise analysis of an electro-optic (EO) sensor system based on experimental and simulation results. We developed a polarization simulator of the EO sensor system using the Jones vector and matrix. The polarization simulator included not only the laser intensity noise but also the laser polarization noise. The polarization noise was converted into an intensity noise due to the polarization noise using a polarizer after the laser source. We proposed a method to adjust differential balance using phasor diagram. The method is used for analysis of the noise characteristics. We expected that the existence of the laser polarization noise can be demonstrated by our experimental setup with and without the polarizer after the laser source. The noise characteristics of experimental results more than 4 kHz agreed with the simulation results under considering the effect of a receiver noise. However, the noise characteristics less than 4 kHz did not agree with simulation results. It was found that the noise characteristics less than 4 kHz are caused by the light intensity unbalance between p- and s- polarized light in our system.

There has been a surge of emphasis on polarimetric imaging modalities recently, in which Mueller matrix polarimetry (MMP) is at the heart of our understanding of polarization properties of an imaged sample. However, the historiography of MMP, predominantly undertaken in optics, largely lost sight of the potential of terahertz radiation on interactions with the imaged samples, especially biological ones. In addition, studies of MMP are generally concerned with intensity-only measurements requiring at least 16 polarization combinations, which dramatically add to the time cost in the process of measurements. The proposed study sets out to examine the complete 4 × 4 MMP from 0.2 to 1 THz using only orthogonal polarizations for two-dimensional (2-D) and 3-D imaging on leaf. A modified THz time domain spectrometer with self-designed linear polarizers is utilized for measurements and data acquisition. The Mueller matrix polar decomposition and Mueller matrix transform are employed to facilitate extraction of polarization characteristics of the imaged leaf. The time-of-flight technique is adopted to assist in the 3-D reconstruction of the leaf. The results demonstrate the effectiveness and feasibility of the novel measurement synthesis approach and the modified system for accurate characterization of the sample. Meanwhile, the findings indicate that MMP is superior in feature extraction as well as contrast enhancement of the sample. The insights gained from this article may be of assistance to the characterization of biological samples with MMP at higher frequencies for future research.

This article presents the results of numerical simulation and optimization of electromagnetic characteristics of a new waveguide polarizer design containing a conducting diaphragm and pins. The the...

The angle of the polarization (AOP) and the degree of polarization (DOP) of the scattered skylight are symmetrically distributed concerning the solar meridian. Based on the symmetry of the skylight polarization distribution pattern, this paper proposes a novel skylight orientation sensor consisting of a camera, an S-waveplate, and a linear polarizer. The skylight orientation sensor is using the image polarization encoding capability of the S-waveplate and the linear polarizer to convert the skylight polarization information into the image’s symmetry axis extraction, which has the advantages of simple structure, better real-time performance, no resolution loss and instantaneous field of view error. The symmetry axis in the image is consistent with the solar meridian. Therefore, the angle between the solar meridian and the skylight orientation sensor reference axis can be obtained without calculating the polarization information, which shows why the sensor has better real-time performance. The angle measurement accuracy and uncertainty of the skylight orientation sensor are verified by numerical simulation and outdoor experiments. The results demonstrate that the skylight orientation sensor has good application potential in autonomous navigation.

The major axis of the elliptically polarized wave generated by a linearly polarized (LP) radiating source and an artificial anisotropic polarizer has been analyzed in this communication. Both theoretical and experimental results show that the major axis of the elliptically polarized wave generated by such a combination has an angle of 0° or 90° to the E-plane of the LP radiator. The angle between the major axis and the E-plane depends on the phase difference of the two orthogonal electric components after propagating through the polarizer. Measurement has been conducted for verification which covered the entire V-band (50–75 GHz). The result in this communication provides instructions for the usage of artificial anisotropic polarizers in detection and measurement, such as the calculation of the polarization efficiency during transmission.

In many optics applications, it is important to use well-polarized light. However, there are situations in which randomly polarized light has distinct advantages. We demonstrate two approaches by which a polarized light beam can be totally depolarized, each using a simple setup and inexpensive components. The first method, designed for narrow spectrum light, works by combining the horizontal polarization component of the beam with the delayed vertical component. The second method, which is most suitable for broad spectrum light, uses birefringent quartz plates. In both approaches, the polarization state is characterized by Stokes parameters measured using a rotating quarter-wave plate and fixed polarizer. We measure the coherence function of the electric fields and determine the minimum delay or quartz plate thickness required for decoherence. Coherences are modelled by Gaussian or Lorentzian functions and compared with the spectral properties of the light sources.

Fabrication method of a fiber optic electric field sensing probe using polarization maintaining fiber (PMF) is described including a birefringent axes aligning system. The sensing probe is basically a fiber-coupled Fabry-Perot resonator where a thin birefringent wafer of LiTaO3 with an external cavity is mounted onto the end of PMF. An optical wave from a superluminescent laser diode after a linear polarizer parallel to the slow axis of the PMF is made to enter the LiTaO3 crystal with polarization parallel to its extraordinary axis and the reflected optical wave is detected after passing through a polarization analyzer. By measuring a minimum value of a ratio of the reflected optical power at 90° to that of 0° of analyzer, we successfully demonstrated that the angular accuracy of the slow axis of the PMF with respect to the extraordinary axis of the LiTaO3 can be evaluated. Aligning both axes precisely, the electro-optic effect associated with LiTaO3 and polarization is optimized with greater stability. Long term stability of the fabricated PMF sensing probe was enhanced by about 3 times compared to that of a conventional single mode fiber one. As a result of uncertainty analysis, the method we proposed has an overall angular uncertainty of 1° when the used fiber optic components have polarization angle tolerance of 1°.

A new compact static wind imaging interferometer, called the Birefringent Doppler Wind Imaging Interferometer (BIDWIN), has been developed for the purpose of observing upper atmospheric winds using suitably isolated airglow emissions. The instrument combines a field-widened birefringent delay plate placed between two crossed Wollaston prisms with an imaging system, waveplates and polarizers to produce four fixed 90∘ phase-stepped images of the interference fringes conjugate to the scene of interest. A four-point algorithm is used to extract line-of-sight Doppler wind measurements across the image of the scene. The arrangement provides a similar throughput to that of a field-widened Michelson interferometer; however, the interferometric component of BIDWIN is smaller, simpler to assemble and less complicated to operate. Consequently, the instrument provides a compact, lightweight and robust alternative that can be constructed and operated with lower cost. In this paper, the instrument concept is presented, and the design and optimization of a prototype version of the instrument are discussed. Characterization of the lab prototype is presented, and the performance of the instrument is examined by applying the instrument to measure a low-velocity two-dimensional Doppler wind field with a high precision (5 m s−1) in the lab.

In this letter, a multibeam transmitarray carrying orbital angular momentum (OAM) is introduced to realize 1-D +/−30° beam coverage. A three-layer unit cell is designed to provide high-efficiency transmission and full 360° phase coverage. This unit cell consists of two orthogonal polarizers at the outermost layers and a polarization rotating patch in the middle layer. A feeding array is employed to illuminate the transmitarray. By combining bifocal principle with the method of OAM beam generation, the stability of steered OAM beams is improved compared to conventional single focal design. A five-beam protype producing −1 OAM mode is simulated, fabricated, and measured, realizing a +/−30° beam coverage with stable vortex property and high mode purity. The proposed design has advantages such as multi-OAM-beam, stable vortex property, wideband, high gain, and easy fabrication.

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.

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.

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 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°.

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°.

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.

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.

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.

Polarization plays a key role in science; hence its versatile manipulation is crucial. Existing polarization optics, however, can only manipulate polarization in a single transverse plane. Here we demonstrate a new class of polarizers and wave plates—based on metasurfaces—that can impart an arbitrarily chosen polarization response along the propagation direction, regardless of the incident polarization. The underlying mechanism relies on transforming an incident waveform into an ensemble of pencil-like beams with different polarization states that beat along the optical axis thereby changing the resulting polarization at will, locally, as light propagates. Remarkably, using form-birefringent metasurfaces in combination with matrix-based holography enables the desired propagation-dependent polarization response to be enacted without a priori knowledge of the incident polarization—a behaviour that would require three polarization-sensitive holograms if implemented otherwise. Our work expands the use of polarization in the design of multifunctional metasurfaces and may find application in tunable structured light, optically switchable devices and versatile light–matter interactions. Using a metasurface that allows shaping of the polarization state of a light beam independently at each point of space along its propagation direction, longitudinally variable polarization optical components are demonstrated, inspiring new directions in structured light, polarization-switchable devices and light–matter interaction.

A high-sensitivity temperature sensor based on reflective Solc-like filter with Vernier effect has been proposed and experimentally investigated in this article. The reflective Solc-like filter is composed of a polarizer and the cascaded polarization maintaining fibers (PMFs) of similar length, which is a kind of all-fiber polarization interference filter. The gold film is coated in the end of the longer PMF to improve the reflectivity of the filter. The mathematical model of the reflective Solc-like filter has been built by the Jones matrix. The simulation results show that the main factor affecting the temperature sensitivity is the length of the PMF fiber, and the fringe visibility of the spectral fringes is only related to splice angles. Experiment results indicate that the Solc-like filter exhibits a high sensitivity of −44.27 nm/°C, which is enlarged over 25 times compared with that of the reflective Solc filter with single PMF, and the temperature resolution can reach $4.5\times 10^{{-4{ }}\,\circ }\text{C}$ . To the best of our knowledge, this is the first demonstration that the cascaded PMFs have been applied to the reflective filter, which provides high reference value for the application of polarization interference filters in the sensing field.

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.

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.

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.

In this paper, a dual circularly-polarized multilayer reflective surface (MRS) based on loaded ring-slots for reflectarray applications is presented. The MRS comprises a wideband multilayer circular polarizer cascaded with a multilayer reflective screen with independent phase shifting properties for the two orthogonal linearly polarized components. The first polarization conversion is accomplished by a four-layer polarizer based on periodic arrays of bisected split rings that converts two incident circularly-polarized waves, one left-handed (LHCPW) and other right-handed (RHCPW), into two linearly polarized waves with orthogonal polarization planes. These two waves can be phase-shifted independently by a periodic two-layer array of specially designed reflective elements. Each element consists of a ring-slot resonator loaded with two pairs of reactances orthogonally located that can be varied to obtain two linear reflection phase tapers along the array. These reflected waves are then transformed back by the polarizer into two circularly polarized waves traveling into the desired directions. To validate the proposed approach, a six-layer prototype operating at 32 GHz that provides reflection elevation and azimuthal angles for the RHCPW at 22° and 180°, respectively, and reflection elevation and azimuthal angles for the LHCPW at 18° and 0°, respectively, has been designed, fabricated, and experimentally verified.

In this paper, a microwave polarizer based on frequency selective surface (FSS) loaded with complementary split ring resonator (CSRR) for non-planar and conformal application is presented. The frequency-selective polarizer is fabricated on liquid crystal polymer substrates (LCPs) material with $50\mu \text{m}$ thickness, which shows very good mechanical flexibility for microwave band. The Frequency-selective polarizer consists of a metal FSS screen pair with double complementary split ring resonators aligned in the vertical direction without any displacement. The substrate integrated waveguide (SIW) cavity was introduced to enhance the Q-factor of the CSRR particles and the mechanical strength of the FSS screens at bending conditions. The measured results show that the CSSR-FSS polarizer with the minimum transmission loss for TE-polarization incidence wave is 0.75dB at the 10.24 GHz and 19.05 dB for TM-polarization incidence wave, with an extinction ratio of 18.3dB. Finally, the oblique incidence from normal to 60 degrees and bending tests with the bending radius of 9.8 cm and 8.8 cm of the CSRR-FSSs were also carried out, and the measured results indicate that the CSRR-FSS show a low susceptibility to bending behavior at the small bending radius beyond the 8.8 cm and different incidence angles from normal to 45 degrees. Both the simulated and experiment data indicated that the proposed ultra-thin CSRR-FSS shows excellent flexibility and polarization selectivity.

In this paper, a circularly polarized Transmitarray antenna design for the Ku-band frequency range is presented. The transmitarray antenna with 121 elements is designed using a four-layer double square ring with a center patch unit cell. The Unit cell parametric analysis shows a high transmission coefficient magnitude of −1.26 dBi and a wide phase range of 256 degrees. A meander line polarizer is designed at 12GHz to convert the polarization from linear to circular. This meander line polarizer is placed in front of the horn antenna as a superstrate layer. The final measurement results show a high gain circular polarized TA antenna with a maximum gain of 20.17dBic and a value of 1.89 for the axial ratio is achieved at 11.2 GHz. The 1dB antenna gain and 3-dB axial ratio bandwidth are calculated as 0.65GHz and 1.07GHz, respectively. The proposed design offers a low profile and less complex structure, making it suitable for long-range communication systems, especially in Ku band applications.

A broadband and wide-angle scanning linear polarization (LP)-to-circular polarization (CP) converter based on a dual-layer structure is presented. The elementary cell is composed of conventional Jerusalem crosses (JCs). The design procedure is based on transmission line circuit model and on full-wave simulations. The proposed equivalent circuit has been generalized to include the oblique incidence in the model. Simulated results demonstrate a 24% axial ratio bandwidth for an incidence angle $\theta = \pm 50^{\circ }$ in both x z and y z planes. The proposed converter provides a unique combination of wide bandwidth, thin profile, and stable response with respect to the angle of incidence. It can be integrated into any LP antenna system to generate CP without significantly affecting the antenna performances.

Light polarization could provide critical visual information (e.g., surface roughness, geometry, or orientation) of the imaged objects beyond prevailing signals of intensity and wavelength. The polarization imaging technology thus has a large potential in broad fields such as object detection. However, intricate polarization coding is often required in these fields, and the existing complicated lensed system and polarizers have limited the miniaturization capabilities of the integrated imaging sensor. In this study, we demonstrate the utilization of two-dimensional (2D) in-plane anisotropic α-GeSe semiconductor to realize the polarizer-free polarization-sensitive visible/near-infrared (VIS-NIR) photodetector/imager. As the key part of the sensor system, this prototype Au/GeSe/Au photodetector exhibits impressive performances in terms of high sensitivity, broad spectral response, and fast-speed operation (∼103 AW−1 400–1050 nm, and 22.7/49.5 µs). Further, this device demonstrates unique polarization sensitivity in the spectral range of 690–1050 nm and broadband absorption of light polarized preferentially in the γ-direction, as predicted by the analysis of optical transition behavior in α-GeSe. Then we have successfully incorporated the 2D GeSe device into an imaging system for the polarization imaging and captured the polarization information of the radiant target with a high contrast ratio of 3.45 at 808 nm (NIR band). This proposed imager reveals the ability to sense dual-band polarization signals in the scene without polarizers and paves the way for polarimetric imaging sensor arrays for advanced applications.

Simultaneous application of polarization microscopy and Interphako interference contrast has been used to study the internal structure of algal cells. The interference contrast technique showed fine cell structures (important is the selection of interference colors according to the Mach-Zehnder interferometer setting). In a polarization microscope, the crossed polarization filters together with the first-order quartz compensator mounted turntable showed the maximum birefringence of the individual structures. Material containing green algae was collected in the villages Sýkořice and Zbečno, Protected Landscape Area (PLA) Křivoklátsko. The objects were studied in a Carl Zeiss Jena NfpK laboratory microscope equipped with an In 160 base body with an Interphako In contrast interference module including a Mach-Zehnder interferometer with variable phase contrast, a special condenser with interchangeable aperture plates, a turntable, a Meopta Praha polarizer, a LOMO Sankt Petersburg analyzer, and a quartz compensator with first-order red and the digital camera DSLR Nikon D 70. Green algae of three orders were studied: Siphonocladales, Zygnematales, and Desmidiales. Anisotropic structures were found in all studied representatives of the green algae of the phylum Chlorophyta. Especially their cell walls showed strong birefringence (in all representatives of these orders). On the other hand, a representative of the order Siphonocladales (the genus Cladophora, Cladophoraceae, Ulvophyceae) was rarely found to display weak birefringent granules of storage substances due to the setting of the Mach-Zehnder interferometer and the use of the first-order compensator (interference colors are intensified). In addition, a very weak birefringence of periphyton cells (microbial biofilm) was found. In the study of the second algae of the genus Spirogyra (Zygnemataceae, Zygnematales, Conjugatophyceae), a strongly birefringent connecting wall between algal cells was found in contrast to the weaker birefringence of the peripheral wall. It was the use of Interphako interference contrast together with polarization filters and a first-order quartz compensator that particularly emphasized the central part of the connecting wall. In the study of the twinned Pleurotaenium algae (Desmidiaceae, Desmidiales, Conjugatophyceae), a strongly birefringent wall was found along the periphery of the cell with a nucleus in the middle part (isthmus). In this narrowing in the center of the cell, a sharply delimited birefringent edge of the cell wall is visible, especially when using Interphako interference contrast along with crossed polarization filters and a first-order quartz compensator. In conclusion, Interphako interference contrast provides a high degree of image contrast in a microscope and, if suitably simultaneously complemented by polarization microscopy (including a first-order quartz compensator), it will allow us to infer some of the composition of the investigated structures. However, working with Interphako interference contrast is considerably more difficult (setting Mach-Zehnder interferometer) than using other contrast techniques (positive and negative phase contrast, color contrast, relief contrast, and dark field).

In this letter, a high-performance dual circularly polarized (CP) circular waveguide horn antenna operating in the V -band (54–60 GHz) is analyzed, built, and tested. The antenna is designed from a cylindrical waveguide section and consists of two mutually orthogonal side-fed ports, a mono-groove, and a conical horn section. The mono-groove is an annulus sector placed at 45° with respect to both the input ports and provides a phase delay of 90° to generate right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). Simulation results show that the proposed CP horn antenna has interport isolation more than 15 dB, axial ratio (AR) below 2.2 dB, and polarization isolation over 25 dB in the impedance matching bandwidth from 54 to 60 GHz. Also, the proposed antenna provides symmetric radiation patterns. A prototype of this antenna has been fabricated using computer numerical control (CNC) machining technique. The experimental results show good agreement with the simulation results.

A circularly polarized (CP) scanning phased array antenna based on circular polarizer is proposed. An efficient technique is developed to introduce the novel scheme of the designed patch antenna an...