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Keywords = mirror and circular symmetry

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14 pages, 3371 KiB  
Article
A Symmetry-Driven Broadband Circularly Polarized Magnetoelectric Dipole Antenna with Bandpass Filtering Response
by Xianjing Lin, Zuhao Jiang, Miaowang Zeng and Zengpei Zhong
Symmetry 2025, 17(7), 1145; https://doi.org/10.3390/sym17071145 - 17 Jul 2025
Viewed by 176
Abstract
This paper presents a symmetry-driven broadband circularly polarized magnetoelectric dipole antenna with bandpass filtering response, where the principle of symmetry is strategically employed to enhance both radiation and filtering performance. The antenna’s circular polarization is achieved through a symmetrical arrangement of two orthogonally [...] Read more.
This paper presents a symmetry-driven broadband circularly polarized magnetoelectric dipole antenna with bandpass filtering response, where the principle of symmetry is strategically employed to enhance both radiation and filtering performance. The antenna’s circular polarization is achieved through a symmetrical arrangement of two orthogonally placed metallic ME dipoles combined with a phase delay line, creating balanced current distributions for optimal CP characteristics. The design further incorporates symmetrical parasitic elements—a pair of identical inverted L-shaped metallic structures placed perpendicular to the ground plane at −45° relative to the ME dipoles—which introduce an additional CP resonance through their mirror-symmetric configuration, thereby significantly broadening the axial ratio bandwidth. The filtering functionality is realized through a combination of symmetrical modifications: grid slots etched in the metallic ground plane and an open-circuited stub loaded on the microstrip feed line work in tandem to create two radiation nulls in the upper stopband, while the inherent symmetrical properties of the ME dipoles naturally produce a radiation null in the lower stopband. This comprehensive symmetry-based approach results in a well-balanced bandpass filtering response across a wide operating bandwidth. Experimental validation through prototype measurement confirms the effectiveness of the symmetric design with compact dimensions of 0.96λ0 × 0.55λ0 × 0.17λ0 (λ0 is the wavelength at the lowest operating frequency), demonstrating an impedance bandwidth of 66.4% (2.87–5.05 GHz), an AR bandwidth of 31.9% (3.32–4.58 GHz), an average passband gain of 5.5 dBi, and out-of-band suppression levels of 11.5 dB and 26.8 dB at the lower and upper stopbands, respectively, along with good filtering performance characterized by a gain-suppression index (GSI) of 0.93 and radiation skirt index (RSI) of 0.58. The proposed antenna is suitable for satellite communication terminals requiring wide AR bandwidth and strong interference rejection in L/S-bands. Full article
(This article belongs to the Special Issue Symmetry Study in Electromagnetism: Topics and Advances)
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13 pages, 4788 KiB  
Article
Design of High-Efficiency Circularly Polarized Reflection Mirror Based on Chiral Dielectric Metasurface
by Bo Cheng, Yuxiao Zou, Kunpeng Zhai and Guofeng Song
Photonics 2025, 12(4), 341; https://doi.org/10.3390/photonics12040341 - 3 Apr 2025
Viewed by 554
Abstract
Circularly polarized lasers can directly generate circularly polarized light without requiring complex external optics, enabling applications in biosensing, environmentally friendly antibacterial treatments, and cancer cell phototherapy. However, the circular dichroism (CD) of chiral metasurface mirrors—a core component of such lasers—typically remains below 3%, [...] Read more.
Circularly polarized lasers can directly generate circularly polarized light without requiring complex external optics, enabling applications in biosensing, environmentally friendly antibacterial treatments, and cancer cell phototherapy. However, the circular dichroism (CD) of chiral metasurface mirrors—a core component of such lasers—typically remains below 3%, limiting beam quality. Using COMSOL simulations, we broke the metasurface’s structural symmetry via displacement and rotation operations, introducing chirality to the unit cell. At 980 nm, the metasurface achieved 99.85% reflectivity and 52% CD. Multipole analysis suggests this enhancement stems from electric dipole and quadrupole coupling. Our laser design could generate micro-nano-scale chiral light, advancing applications in biophotonics, biomedicine, and life sciences. Full article
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47 pages, 8145 KiB  
Article
Nuclear-Spin-Dependent Chirogenesis: Hidden Symmetry Breaking of Poly(di-n-butylsilane) in n-Alkanes
by Michiya Fujiki, Takashi Mori, Julian R. Koe and Mohamed Mehawed Abdellatif
Symmetry 2025, 17(3), 433; https://doi.org/10.3390/sym17030433 - 13 Mar 2025
Viewed by 2088
Abstract
Since the 1960s, theorists have claimed that the electroweak force, which unifies parity-conserving electromagnetic and parity-violating weak nuclear forces, induces tiny parity-violating energy differences (10−10–10−21 eV) between mirror-image molecules. This study reports the dual mirror-symmetry-breaking and second-order phase transition characteristics [...] Read more.
Since the 1960s, theorists have claimed that the electroweak force, which unifies parity-conserving electromagnetic and parity-violating weak nuclear forces, induces tiny parity-violating energy differences (10−10–10−21 eV) between mirror-image molecules. This study reports the dual mirror-symmetry-breaking and second-order phase transition characteristics of mirror-symmetric 73-helical poly(di-n-butylsilane) in n-alkanes under static (non-stirring) conditions. In particular, n-dodecane-h26 significantly enhances the circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. A new (−)-CD band emerges at 299 nm below TC1 ~ 105 °C, with a helix–helix transition at TC2 ~ 28 °C, and exhibits gabs = +1.3 × 10−2 at −10 °C. Synchronously, the CPL band at 340 nm exhibiting glum = −0.7 × 10−2 at 60 °C inverts to glum = +2.0 × 10−2 at 0 °C. Interestingly, clockwise and counterclockwise stirring of the mixture induced non-mirror-image CD spectra. n-Dodecane-d26 weakens the gabs values by an order of magnitude, and oppositely signed CD and a lower TC1 of ~45 °C are observed. The notable H/D isotope effect suggests that the CH3 termini of the polysilane and n-dodecane-h26, which comprise a three identical nuclear spin-1/2 system in a triple-well potential, effectively work as unidirectional hindered rotors due to the handedness of nuclear-spin-dependent parity-violating universal forces. This is supported by the (−)-sign vibrational CD bands in the symmetric and asymmetric bending modes of the CH3 group in n-dodecane-h26. Full article
(This article belongs to the Special Issue Chemistry: Symmetry/Asymmetry—Feature Papers and Reviews)
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14 pages, 4067 KiB  
Article
Spherical Amides with C3 Symmetry: Improved Synthetic Approach and Structural/Optical Analysis
by Daiki Koike, Hyuma Masu, Haruka Uno, Shoko Kikkawa, Hidemasa Hikawa and Isao Azumaya
Molecules 2025, 30(5), 1074; https://doi.org/10.3390/molecules30051074 - 26 Feb 2025
Viewed by 571
Abstract
A spherical amide with C3 symmetry was synthesized by a one-step cyclization reaction using triphenylphosphine and hexachloroethane as coupling reagents. This method enabled synthesis of N-benzyl and N-allyl derivatives, which could not be obtained by the previously reported method. The [...] Read more.
A spherical amide with C3 symmetry was synthesized by a one-step cyclization reaction using triphenylphosphine and hexachloroethane as coupling reagents. This method enabled synthesis of N-benzyl and N-allyl derivatives, which could not be obtained by the previously reported method. The optical resolution of each compound was measured, and their electronic circular dichroism spectra revealed that they were mirror images. The high structural symmetry resulted in a higher Δε (molar absorption difference against right or left circular polarization: εLεR value compared to that of another structural isomer synthesized previously. The absolute structure of the enantiopure crystal of the N-benzyl derivative was determined using the Flack parameter obtained by X-ray crystallographic analysis. Full article
(This article belongs to the Section Organic Chemistry)
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10 pages, 717 KiB  
Article
A New Sum-Channel Radiating Element for a Patch-Monopole Monopulse Feed
by Peter Miklavčič and Boštjan Batagelj
Electronics 2024, 13(16), 3187; https://doi.org/10.3390/electronics13163187 - 12 Aug 2024
Cited by 3 | Viewed by 1171
Abstract
This article describes a new design for the sum-channel, circularly-polarized, radiating patch element of a multimode patch-monopole monopulse feed. Such feeds are suitable for the prime-focus illumination of a deep symmetric reflector. A relatively simple and compact feed design allows for a compact [...] Read more.
This article describes a new design for the sum-channel, circularly-polarized, radiating patch element of a multimode patch-monopole monopulse feed. Such feeds are suitable for the prime-focus illumination of a deep symmetric reflector. A relatively simple and compact feed design allows for a compact single-mirror antenna with monopulse tracking. The feed is about a wavelength in diameter, also making it suitable for illuminating smaller antennas, for example, in LEO-satellite ground (client) stations. The design applies a slotted circular patch as a circularly-polarized sum-channel element. The design variables are optimized mainly for the sum-channel aperture illumination efficiency in an S-band satellite ground station. After a few cut-and-try iterations, the final feed prototype was produced and measured. In addition to an additional degree of freedom in the geometry and potentially easier fabrication, the new sum-channel radiating-element shape allows for a slightly better monopulse channel isolation, and a higher radiation-pattern symmetry compared to the previous design. Full article
(This article belongs to the Special Issue Antenna Designs for 5G/IoT and Space Applications, 2nd Edition)
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19 pages, 5164 KiB  
Article
An Improved Grey Wolf Optimizer with Multi-Strategies Coverage in Wireless Sensor Networks
by Yun Ou, Feng Qin, Kai-Qing Zhou, Peng-Fei Yin, Li-Ping Mo and Azlan Mohd Zain
Symmetry 2024, 16(3), 286; https://doi.org/10.3390/sym16030286 - 1 Mar 2024
Cited by 28 | Viewed by 2625
Abstract
For wireless sensor network (WSN) coverage problems, since the sensing range of sensor nodes is a circular area with symmetry, taking symmetry into account when deploying nodes will help simplify problem solving. In addition, in view of two specific problems of high node [...] Read more.
For wireless sensor network (WSN) coverage problems, since the sensing range of sensor nodes is a circular area with symmetry, taking symmetry into account when deploying nodes will help simplify problem solving. In addition, in view of two specific problems of high node deployment costs and insufficient effective coverage in WSNs, this paper proposes a WSN coverage optimization method based on the improved grey wolf optimizer with multi-strategies (IGWO-MS). As far as IGWO-MS is concerned, first of all, it uses Sobol sequences to initialize the population so that the initial values of the population are evenly distributed in the search space, ensuring high ergodicity and diversity. Secondly, it introduces a search space strategy to increase the search range of the population, avoid premature convergence, and improve search accuracy. And then, it combines reverse learning and mirror mapping to expand the population richness. Finally, it adds Levy flight to increase the disturbance and improve the probability of the algorithm jumping out of the local optimum. To verify the performance of IGWO-MS in WSN coverage optimization, this paper rasterizes the coverage area of the WSN into multiple grids of the same size and symmetry with each other, thereby transforming the node coverage problem into a single-objective optimization problem. In the simulation experiment, not only was IGWO-MS selected, but four other algorithms were also selected for comparison, namely particle swarm optimization (PSO), grey wolf optimizer (GWO), grey wolf optimization based on drunk walk (DGWO), and grey wolf optimization led by two-headed wolves (GWO-THW). The experimental results demonstrate that when the number of nodes for WSN coverage optimization is 20 and 30, the optimal coverage rate and average coverage rate using IGWO-MS are both improved compared to the other four comparison algorithms. To make this clear, in the case of 20 nodes, the optimal coverage rate of IGWO-MS is increased by 13.19%, 1.68%, 4.92%, and 3.62%, respectively, compared with PSO, GWO, DGWO, and GWO-THW; while IGWO-MS performs even better in terms of average coverage rate, which is 16.45%, 3.13%, 11.25%, and 6.19% higher than that of PSO, GWO, DGWO, and GWO-THW, respectively. Similarly, in the case of 30 nodes, compared with PSO, GWO, DGWO, and GWO-THW, the optimal coverage rate of the IGWO-MS is increased by 15.23%, 1.36%, 5.55%, and 3.66%; the average coverage rate is increased by 16.78%, 1.56%, 10.91%, and 8.55%. Therefore, it can be concluded that IGWO-MS has certain advantages in solving WSN coverage problems, which is reflected in that not only can it effectively improve the coverage quality of network nodes, but it also has good stability. Full article
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29 pages, 16443 KiB  
Review
Chiral Metasurfaces: A Review of the Fundamentals and Research Advances
by Semere Araya Asefa, Sangmin Shim, Myeongsu Seong and Dasol Lee
Appl. Sci. 2023, 13(19), 10590; https://doi.org/10.3390/app131910590 - 22 Sep 2023
Cited by 31 | Viewed by 8005
Abstract
Chirality, the absence of mirror symmetry, is predominant in nature. The chiral nature of the electromagnetic field behaves differently with chiral matter for left circularly polarized and right circularly polarized light. The chiroptical behavior in the sensing of naturally occurring chiral objects is [...] Read more.
Chirality, the absence of mirror symmetry, is predominant in nature. The chiral nature of the electromagnetic field behaves differently with chiral matter for left circularly polarized and right circularly polarized light. The chiroptical behavior in the sensing of naturally occurring chiral objects is weak, and improving the chiroptical response enhances the chiral sensing platform. This review covers the fundamental concepts of chiral metasurfaces and various types of single- and multi-layered chiral metasurfaces. In addition, we discuss tunable and deep-learning-based chiral metasurfaces. Tunability is achieved by manipulating the meta-atom’s property in response to external stimuli for applications such as optical modulation, chiral photonics, advanced sensing, and adaptive optics. Deep-learning modeling techniques, such as CNNs and GANs, offer efficient learning of the complex relationships in data, enabling the optimization and accurate prediction of chiral metasurface properties. The challenges in the design and fabrication of chiral metasurface include achieving broadband performance and scalability and addressing material limitations. Chiral metasurface performance is evaluated by optical rotation, circular dichroism enhancement, and tunability, which are quantified through the spectroscopic measurement of circular dichroism and optical rotation. Chiral metasurface progress enables applications, including metaholography, metalenses, and chiral sensing. Chiral sensing improves the detection of pharmaceuticals and biomolecules, increasing the sensitivity and accuracy of analytical diagnostics. Full article
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13 pages, 2794 KiB  
Article
Chiral Quasi-Bound States in the Continuum of a Dielectric Metasurface for Optical Monitoring and Temperature Sensing
by Xu Du, Suxia Xie, Haoxuan Nan, Siyi Sun, Weiwei Shen, Jingcheng Yang and Xin Guan
Photonics 2023, 10(9), 980; https://doi.org/10.3390/photonics10090980 - 28 Aug 2023
Cited by 11 | Viewed by 2878
Abstract
Chiral BIC can reach ultrahigh quality factors (Q-factor) based on its asymmetry, with broken mirror symmetries and in-plane inversion. Only by in-plane structural perturbation can chiral quasi-BIC (q-BIC) appear, so it is much more realizable and reasonable for the manufacturers in practical productions [...] Read more.
Chiral BIC can reach ultrahigh quality factors (Q-factor) based on its asymmetry, with broken mirror symmetries and in-plane inversion. Only by in-plane structural perturbation can chiral quasi-BIC (q-BIC) appear, so it is much more realizable and reasonable for the manufacturers in practical productions and fabrications considering the technology and means that are available. In this paper, we design a new dielectric metasurface employing H-shaped silica meta-atoms in the lattice, which is symmetrical in structure, obtaining chiral BIC with ultrahigh Q-factor (exceeding 105). In this process, we change the length of the limbs of the structure to observe the specific BICs. Previous scholars have focused on near-infrared-wavelength bands, while we concentrate on the terahertz wavelength band (0.8–1 THz). We found that there is more than one BIC, thus realizing multiple BICs in the same structure; all of them exhibit excellent circular dichroism (CD) (the maximum value of CD is up to 0.8127) for reflectance and transmittance, which provides significant and unique guidance for the design of multi-sensors. Meanwhile, we performed temperature sensing with chiral BIC; the sensitivity for temperature sensing can reach 13.5 nm/°C, which exhibits high accuracy in measuring temperature. As a consequence, the result proposed in this study will make some contributions to advanced optical imaging, chiral sensors with high frequency and spectral resolution, optical monitoring of environmental water quality, multiple sensors, temperature sensing, biosensing, substance inspection and ambient monitoring and other relevant optical applications. Full article
(This article belongs to the Special Issue Optical Metasurfaces: Recent Advances and Future Directions)
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10 pages, 2401 KiB  
Article
A Single-Celled Metasurface for Multipolarization Generation and Wavefront Manipulation
by Ruonan Ji, Xin Guo, Zhichao Liu, Xianfeng Wu, Chuan Jin, Feng Liu, Xinru Zheng, Yang Sun and Shaowei Wang
Nanomaterials 2022, 12(23), 4336; https://doi.org/10.3390/nano12234336 - 6 Dec 2022
Viewed by 2032
Abstract
Due to their unprecedented ability to flexibly manipulate the parameters of light, metasurfaces offer a new approach to integrating multiple functions in a single optical element. In this paper, based on a single-celled metasurface composed of chiral umbrella-shaped metal–insulator–metal (MIM) unit cells, a [...] Read more.
Due to their unprecedented ability to flexibly manipulate the parameters of light, metasurfaces offer a new approach to integrating multiple functions in a single optical element. In this paper, based on a single-celled metasurface composed of chiral umbrella-shaped metal–insulator–metal (MIM) unit cells, a strategy for simultaneous multiple polarization generation and wavefront shaping is proposed. The unit cells can function as broadband and high-performance polarization-preserving mirrors. In addition, by introducing a chiral-assisted Aharonov–Anandan (AA) geometric phase, the phase profile and phase retardation of two spin-flipped orthogonal circular polarized components can be realized simultaneously and independently with a single-celled metasurface via two irrelevant parameters. Benefiting from this flexible phase manipulation ability, a vectorial hologram generator and metalens array with spatially varying polarizations were demonstrated. This work provides an effective approach to avoid the pixel and efficiency losses caused by the intrinsic symmetry of the PB geometric phase, and it may play an important role in the miniaturization and integration of multipolarization-involved displays, real-time imaging, and spectroscopy systems. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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14 pages, 6986 KiB  
Article
Plasmonic Sensing and Switches Enriched by Tailorable Multiple Fano Resonances in Rotational Misalignment Metasurfaces
by Xiaofeng Xu, Xiao-Qing Luo, Qinke Liu, Yan Li, Weihua Zhu, Zhiyong Chen, Wuming Liu and Xin-Lin Wang
Nanomaterials 2022, 12(23), 4226; https://doi.org/10.3390/nano12234226 - 28 Nov 2022
Cited by 5 | Viewed by 2147
Abstract
Fano resonances that feature strong field enhancement in the narrowband range have motivated extensive studies of light–matter interactions in plasmonic nanomaterials. Optical metasurfaces that are subject to different mirror symmetries have been dedicated to achieving nanoscale light manipulation via plasmonic Fano resonances, thus [...] Read more.
Fano resonances that feature strong field enhancement in the narrowband range have motivated extensive studies of light–matter interactions in plasmonic nanomaterials. Optical metasurfaces that are subject to different mirror symmetries have been dedicated to achieving nanoscale light manipulation via plasmonic Fano resonances, thus enabling advantages for high-sensitivity optical sensing and optical switches. Here, we investigate the plasmonic sensing and switches enriched by tailorable multiple Fano resonances that undergo in-plane mirror symmetry or asymmetry in a hybrid rotational misalignment metasurface, which consists of periodic metallic arrays with concentric C-shaped- and circular-ring-aperture unit cells. We found that the plasmonic double Fano resonances can be realized by undergoing mirror symmetry along the X-axis. The plasmonic multiple Fano resonances can be tailored by adjusting the level of the mirror asymmetry along the Z-axis. Moreover, the Fano-resonance-based plasmonic sensing that suffer from mirror symmetry or asymmetry can be implemented by changing the related structural parameters of the unit cells. The passive dual-wavelength plasmonic switches of specific polarization can be achieved within mirror symmetry and asymmetry. These results could entail benefits for metasurface-based devices, which are also used in sensing, beam-splitter, and optical communication systems. Full article
(This article belongs to the Special Issue Nano-Photonics and Meta-Nanomaterials)
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32 pages, 8924 KiB  
Article
Chirality in the Solid State: Chiral Crystal Structures in Chiral and Achiral Space Groups
by Gerhard H. Fecher, Jürgen Kübler and Claudia Felser
Materials 2022, 15(17), 5812; https://doi.org/10.3390/ma15175812 - 23 Aug 2022
Cited by 72 | Viewed by 11567
Abstract
Chirality depends on particular symmetries. For crystal structures it describes the absence of mirror planes and inversion centers, and in addition to translations, only rotations are allowed as symmetry elements. However, chiral space groups have additional restrictions on the allowed screw rotations as [...] Read more.
Chirality depends on particular symmetries. For crystal structures it describes the absence of mirror planes and inversion centers, and in addition to translations, only rotations are allowed as symmetry elements. However, chiral space groups have additional restrictions on the allowed screw rotations as a symmetry element, because they always appear in enantiomorphous pairs. This study classifies and distinguishes the chiral structures and space groups. Chirality is quantified using Hausdorff distances and continuous chirality measures and selected crystal structures are reported. Chirality is discussed for bulk solids and their surfaces. Moreover, the band structure, and thus, the density of states, is found to be affected by the same crystal parameters as chirality. However, it is independent of handedness. The Berry curvature, as a topological measure of the electronic structure, depends on the handedness but is not proof of chirality because it responds to the inversion of a structure. For molecules, optical circular dichroism is one of the most important measures for chirality. Thus, it is proposed in this study that the circular dichroism in the angular distribution of photoelectrons in high symmetry configurations can be used to distinguish the handedness of chiral solids and their surfaces. Full article
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15 pages, 3396 KiB  
Article
Quasi-Bound States in the Continuum Enabled Strong Terahertz Chiroptical Response in Bilayer Metallic Metasurfaces
by Yaolin Hu, Suxia Xie, Chongjun Bai, Weiwei Shen and Jingcheng Yang
Crystals 2022, 12(8), 1052; https://doi.org/10.3390/cryst12081052 - 28 Jul 2022
Cited by 11 | Viewed by 3746
Abstract
Bound state in the continuum (BIC) as a novel non-radiating state of light in the continuum of propagating modes has received great attention in photonics. Recently, chiral BICs have been introduced in the terahertz regime. However, strong chiroptical effects of transmitted waves remain [...] Read more.
Bound state in the continuum (BIC) as a novel non-radiating state of light in the continuum of propagating modes has received great attention in photonics. Recently, chiral BICs have been introduced in the terahertz regime. However, strong chiroptical effects of transmitted waves remain challenging to achieve in metallic terahertz metasurfaces, especially for intrinsic chirality at normal incidences. Here, we propose a chiral quasi-BIC by simultaneously breaking the out-of-plane mirror and in-plane C2 rotation symmetries in a bilayer metallic metasurface, in which spin-selective terahertz transmittance is successfully realized. Benefiting from the symmetry-protected nature of our proposed BIC, precise tuning of structural parameters can lead to anticipated chiroptical performance. As a degree of freedom, the rotation angle of the split ring gaps can fully determine the handedness, linewidth, and working frequency with strong circular dichroism. Besides, the sensing performance shows a surrounding refractive index sensitivity of 200 GHz/RIU, which is similar to those of previous works based on terahertz metasurfaces. Taking advantage exclusively of symmetry-protected BICs to realize transmitted terahertz chiroptical response provides fresh insights into the creation of novel BICs, which enables profound advancements in the surging field of novel terahertz devices. Full article
(This article belongs to the Special Issue Terahertz Metamaterials and Active Modulation)
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15 pages, 26942 KiB  
Article
Characterization of Chirality in Diffractive Metasurfaces by Photothermal Deflection Technique
by Roberto Li Voti, Grigore Leahu, Emilija Petronijevic, Alessandro Belardini, Tiziana Cesca, Carlo Scian, Giovanni Mattei and Concita Sibilia
Appl. Sci. 2022, 12(3), 1109; https://doi.org/10.3390/app12031109 - 21 Jan 2022
Cited by 6 | Viewed by 2785
Abstract
Chirality, a lack of mirror symmetry, is present in nature at all scales; at the nanoscale, it governs the biochemical reactions of many molecules, influencing their pharmacology and toxicity. Chiral substances interact with left and right circularly polarized light differently, but this difference [...] Read more.
Chirality, a lack of mirror symmetry, is present in nature at all scales; at the nanoscale, it governs the biochemical reactions of many molecules, influencing their pharmacology and toxicity. Chiral substances interact with left and right circularly polarized light differently, but this difference is very minor in natural materials. Specially engineered, nanostructured, periodic materials can enhance the chiro-optical effects if the symmetry in their interactions with circular polarization is broken. In the diffraction range of such metasurfaces, the intensity of diffracted orders depends on the chirality of the input beam. In this work, we combine a photothermal deflection experiment with a novel theoretical framework to reconstruct both the thermal and optical behavior of chiro-optical behavior in diffracted beams. Full article
(This article belongs to the Special Issue Optical Chirality: Structures, Detection and Applications)
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8 pages, 2651 KiB  
Article
Fluorescence Spectroscopy of Enantiomeric Amide Compounds Enforced by Chiral Light
by Alessandro Belardini, Emilija Petronijevic, Ramin Ghahri, Daniele Rocco, Fabiana Pandolfi, Concita Sibilia and Leonardo Mattiello
Appl. Sci. 2021, 11(23), 11375; https://doi.org/10.3390/app112311375 - 1 Dec 2021
Cited by 5 | Viewed by 2448
Abstract
Chirality, the absence of mirror symmetry, governs behavior in most biologically important molecules, thus making the chiral recognition of great importance in the pharmaceutical and agrochemical industries, as well as medicine. Chiral molecules can be characterized by means of optical experiments based on [...] Read more.
Chirality, the absence of mirror symmetry, governs behavior in most biologically important molecules, thus making the chiral recognition of great importance in the pharmaceutical and agrochemical industries, as well as medicine. Chiral molecules can be characterized by means of optical experiments based on chiro-optical excitation of molecules. Specifically, chiral absorptive materials differently absorb left- and right-circular polarized light, i.e., they possess circular dichroism (CD). Unfortunately, the natural CD of most molecules is very low and lies in the ultraviolet range. Fluorescence-detected CD is a fast and sensitive tool for investigation of chiral molecules which emit light; ultralow CD in absorption can be detected as the difference in emission. In this work, we perform fluorescence-detected CD on novel chiral amide compounds, designed specifically for visible green emission; we synthesize two enantiomeric fluorescent compounds using low-cost starting compounds and easy purification. We investigate different solutions of the enantiomers at different concentrations, and we show that the fluorescence of the intrinsically chiral compounds depends on the polarization state of the penetrating light, which is absorbed at 400 nm and emits across the green wavelength range. We believe that these compounds can be coupled with plasmonic nanostructures, which further shows promise in applications regarding chiral sensing or chiral emission. Full article
(This article belongs to the Special Issue Optical Chirality: Structures, Detection and Applications)
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14 pages, 23793 KiB  
Article
Mirror and Circular Symmetry of Autofocusing Beams
by Svetlana N. Khonina
Symmetry 2021, 13(10), 1794; https://doi.org/10.3390/sym13101794 - 26 Sep 2021
Cited by 15 | Viewed by 3711
Abstract
This article demonstrates the crucial importance of the symmetrization method for the formation of autofocusing beams. It is possible to impart autofocusing properties to rather arbitrary distributions, for example, truncated and inverted classical modes (such as Hermite–Gaussian, Laguerre–Gaussian, and Bessel modes) or shift [...] Read more.
This article demonstrates the crucial importance of the symmetrization method for the formation of autofocusing beams. It is possible to impart autofocusing properties to rather arbitrary distributions, for example, truncated and inverted classical modes (such as Hermite–Gaussian, Laguerre–Gaussian, and Bessel modes) or shift the fundamental Gaussian beam by inserting mirror or circular symmetry. The most convenient for controlling autofocusing characteristics is the truncated sinus function with a power-law argument dependence. In this case, superlinear chirp beams (with power q > 2) exhibit sudden and more abrupt autofocusing than sublinear chirp beams (with power 1 < q < 2). Comparison of the different beams’ propagation is performed using fractional Fourier transform, which allows obtaining the field distribution in any paraxial region (both in the Fresnel and Fraunhofer diffraction regions). The obtained results expand the capabilities of structured beams in various applications in optics and photonics. Full article
(This article belongs to the Section Computer)
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