Circular polarization

About: Circular polarization is a research topic. Over the lifetime, 15201 publications have been published within this topic receiving 234418 citations.

3D Helix Engineering in Chiral Photonic Materials

Abstract: Engineering the helical structure of chiral photonic materials in three dimensions remains a challenge. 3D helix engineered photonic materials are fabricated by local stratification in a photopolymerizable chiral nematic liquid crystal. The obtained chiral photonic materials reflect both handedness of circular polarized light and show super-reflectivity. Simulations match the experimentally observed photonic properties and reveal a distorted helical structure. 3D engineered polymer films can be made that reflect both left- and right handed circular and linear polarized light dependent and exhibit a changing color contrast upon altering the polarization of incident light. Hence, these 3D engineered photonic materials are of interest for new and emerging applications ranging from anti-counterfeit labels and data encryption to aesthetics and super-reflective films.

Right-Hand/Left-Hand Circularly Polarized High-Gain Antennas Using Partially Reflective Surfaces

Abstract: Single-feed, efficient, high-gain antennas using partially reflective surface (PRS) with right-hand/left-hand circular polarization (CP) are investigated. Metallic ground plane and a PRS with square patch (SP) arrays at about 0.5λ0 height form the Fabry-Perot cavity (FPC) that is fed by a circularly polarized microstrip antenna (MSA). Right-handed circular polarization (RHCP) or left-handed circular polarization (LHCP) at the MSA is obtained using a single diagonal feed and shorting posts along x- or y-axes. Constant high-gain performance is obtained by resonating feed patch (FP) and SP arrays in the same frequency band. The effect of the SP array on antenna performance is critically analyzed. Gain enhancement of 10 dB over the circularly polarized MSA is obtained by optimizing PRS structures. Antennas with different PRSs yield peak gain of 9.1-17.3 dBi, and axial ratio (AR) is less than 3 dB over the desired frequency band. Gain variation is less than 1 dB over the frequency band. Measured results validate the design concept and indicate that the proposed structures exhibit good radiation characteristics and are suitable for satellite systems.

Measurement of the polarization effects of an instrument using partially polarized light

Abstract: Accuracy of a radiometer is adversely affected by scene polarization if the receiving optical system is sensitive to polarization. It is therefore necessary to specify and measure the sensitivity of the system to polarized light. The Mueller-Stokes matrix of an instrument may be determined experimentally and used to predict the effects of the instrument on any beam. The specification of a maximum polarization sensitivity stated in terms of the degree of polarization produced in an unpolarized beam can be experimentally verified even though an unpolarized beam is not available in the laboratory for direct measurement.

Design of Linear-to-Circular Polarization Transformers Made of Long Densely Packed Metallic Helices

Abstract: In this work, we study the realization of realistic polarization transformers formed by long metallic helices. To this end, we propose a new homogenization model to characterize the propagation of electromagnetic waves in a medium formed by infinitely long helices. We derive approximate analytical expressions for the effective permittivity, effective permeability and the magnetoelectric tensor of the composite material, taking into account the effects of spatial dispersion. We apply the new homogenization model to characterize novel linear-to-circular polarization transformers. Our results show that the metamaterial screen may be designed in such a way that an incoming linearly polarized wave may be transformed into a circularly polarized transmitted wave, and that the transmission efficiency of such polarization transformer may be as high as 95%.