A novel metamaterial inspired small array Fabry‐Perot Resonator cavity antenna is designed over a wide‐band dielectric resonator antenna to enhance gain and bandwidth operating at C‐band ...applications. Further, the cavity resonator is modified with the application of 12 no. of RF p‐i‐n diodes between the upper layer of the posterior unit‐cells to achieve the polarization reconfigurability (PR) keeping the bandwidth, gain and efficiency intact. The overall dimension of the proposed antenna is 0.8 λ × 0.8 λ × 0.56 λ. With the PR architecture, the antenna imparts 4.8 GHz bandwidth operating between 4 and 8.8 GHz with an average simulated efficiency of 72% and an average gain of 20 dBi throughout the operating band. The specific alignment of the diode polarity enables the model to obtain left‐handed circular polarization and/or right‐handed circular polarization.
The front cover artwork is provided by the group of Norihisa Kobayashi and Kazuki Nakamura at Chiba University. The image shows the drastic luminescence enhancement and induced circular polarization ...of Eu(D‐facam)3 in the presence of tetramethylammonium acetate. Read the full text of the Article at 10.1002/cphc.202100609.
“We report our investigation into the optical behaviours of chiral Eu(III) complexes in the presence of a series of tetramethylammonium salts in 1‐butanol…” This and more about the story behind the front cover can be found in the Article at 10.1002/cphc.202100609.
We demonstrate that rotationally symmetric chiral metasurfaces can support sharp resonances with the maximum optical chirality determined by precise shaping of bound states in the continuum (BICs). ...Being uncoupled from one circular polarization of light and resonantly coupled to its counterpart, a metasurface hosting the chiral BIC resonance exhibits a narrow peak in the circular dichroism spectrum with the quality factor limited by weak dissipation losses. We propose a realization of such chiral BIC metasurfaces based on pairs of dielectric bars and validate the concept of maximum chirality by numerical simulations.
A dual-band linear-to-circular polarization converter (LCPC) based on a single-layer dielectric substrate is proposed. The element of the converter consists of two identical metallic layers with a ...combination of a connected Jerusalem cross (JC) and an "I"-type dipole for each layer. The proposed converter is designed by using an equivalent circuit model (ECM). Left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) beams can be, respectively, generated at <inline-formula> <tex-math notation="LaTeX">{K} </tex-math></inline-formula>-band and Ka -band excited by a linearly polarized (LP) wave tilted 45° relative to the <inline-formula> <tex-math notation="LaTeX">{x} </tex-math></inline-formula>- and <inline-formula> <tex-math notation="LaTeX">{y} </tex-math></inline-formula>-directions of the converter. In addition, the converter covers two operation bands for <inline-formula> <tex-math notation="LaTeX">{K} </tex-math></inline-formula>-/ Ka -band satellite communications with high conversion efficiency and low polarization extinction ratio (PER). After full-wave optimization, the proposed converter is fabricated and measured. The measured results show a good agreement with the simulated ones. Even though there exists a tradeoff between the angular stability and the bandwidth of the dual-band LCPCs, the measured axial ratio (AR) remains stable in the lower operation band and a slight fluctuation in the higher band with the incident angle of 20°.
A series-fed single-layer dual-circularly polarized slot array antenna fed by a stepped ridge gap waveguide (RGW) is proposed at the 77-GHz band. The antenna generates dual-circularly polarized ...waves, which shows potential to be used in next-generation polarimetric radar for automotive applications. The antenna contains eight columns of linear arrays and two feeding ports for exciting the columns of the slots. The design process and measured results are described in this article. The measured results show that the realized gain of the proposed antenna is above 27.3 dBi and the axial ratio is about 2 dB over the proposed 76-79 GHz with dual-CP patterns. The measured <inline-formula> <tex-math notation="LaTeX">S_{11} </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">S_{22} </tex-math></inline-formula> for the proposed antenna is below −10 dB and the measured port isolation is above 17.5 dB.
The influence of molecular vibrations on circularly polarized luminescence (CPL) in double helicenes DPC and DNH is reported by Tadashi Mori in a Research Article (e202319702). Specifically, in DPC ...(structure depicted in the picture), the study clarifies how structural changes during electronic transitions shape CPL spectra and dissymmetry (g) factor values, and it underscores the noteworthy contribution of Herzberg–Teller effects in enhancing CPL responses.
Helicenes have attracted considerable attention due to their inherent helical chirality and extended π-conjugation. Recently, rapid progress has been witnessed in the preparation of double, triple, ...quadruple, quintuple, and sextuple helicenes, where plural helicene moieties are symmetrically arranged in a single molecule. While synthetic efforts and X-ray crystallographic analyses devoted to these multiple helicenes and theoretical investigations on their isomerization and racemization behaviors have been relatively well documented and reviewed in the literature, the chiroptical properties of the multiple helicities have been somewhat overlooked. This review discourses the cumulative and systematic investigations on the chiroptical properties such as the circular dichroism (CD) and circularly polarized luminescence (CPL) of multiple helicenes. Although the number and structural variations of multiple helicenes reported to date have been fairly limited, this review overviews the current status of the chemistry of multiple helicenes from the viewpoint of chiroptical properties and provides insights into the design principle for advanced chiroptical materials through the proper arrangement of multiple helices, highlighting the impact of the molecular symmetry on the chiroptical responses.
In this article, a compact shared-aperture dual-band dual-circularly polarized waveguide antenna array is presented to achieve high gain and wide bandwidth in full-duplex satellite communication at ...K/Ka-band. The designed antenna array can simultaneously operate at 20 GHz band with right-hand circular polarization (RHCP) radiation and 30 GHz band with left-hand circular polarization (LHCP) radiation. The array is composed of circular polarization (CP) waveguide antenna elements and full-corporate feed networks. The ridged spectrum polarizer is inserted in the square waveguide to form CP radiation in a stepped waveguide antenna element. The sequential rotation technique is adopted in feed networks to further improve CP axial ratio (AR) performance and bandwidth. The prototype of the proposed 4 <inline-formula> <tex-math notation="LaTeX">\times4 </tex-math></inline-formula> antenna array is fabricated and measured for demonstration. Experimental results show that the overlapped bandwidth in terms of reflection coefficients less than −10 dB and AR lower than 2 dB is 18-22 GHz for RHCP radiation in K-band, and the corresponding bandwidth for LHCP radiation in Ka-band is 28-32 GHz. The measured cross-polarization levels are better than 25.82 dB at 20 GHz and 20.25 dB at 30 GHz, and the measured peak gains at K/Ka-band are 23.94 and 26.87 dBic, respectively.
A chirality-assisted phase is introduced to innovatively impose separate phase profiles in two circular polarization (CP) preserving channels, namely, two co-polarized output components under ...left-handed and right-handed circularly polarized (LHCP and RHCP) illuminations. Such a scheme is physically implemented by a proposed multi-layered meta-atom that achieves chiral characteristics by inner twisting angles between adjacent functional elements. A proof-of-concept metasurface is constructed to realize separate holographic images in two polarization-preserved fields with different propagating distances, respectively. In order to achieve sufficient utilization of the two polarization-preserved components, a further approach that can suppress polarization conversion is proposed with a polyatomic unit composed of four separate chiral meta-atoms arranged in a 2 <inline-formula> <tex-math notation="LaTeX">\times</tex-math> </inline-formula> 2 array. A dual-holographic metasurface is designed to impose characters "<inline-formula> <tex-math notation="LaTeX">L</tex-math> </inline-formula>" and "<inline-formula> <tex-math notation="LaTeX">R</tex-math> </inline-formula>" in two co-polarized fields with little energy distributed in corresponding cross-polarized fields. A prototype of the metasurface is fabricated and experimentally measured. The measurements agree well with theoretical predictions and full-wave simulations, showing in the co-polarized field a character "<inline-formula> <tex-math notation="LaTeX">L</tex-math> </inline-formula>" under LHCP incidence and an "<inline-formula> <tex-math notation="LaTeX">R</tex-math> </inline-formula>" under LHCP incidence. The proposed mechanism provides a theoretical foundation for further CP channel expansion and modulations and has great potential in multifunctional antenna design and wireless communications.
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