Article
Optics
Pei-Jung Wu, Wei-Cheng Tsai, Chan-Shan Yang
Summary: In this study, an electrically tunable multi-band terahertz (THz) metamaterial filter based on graphene and multiple-square-loop structures was designed. The structure consists of multiple metal square loops of different sizes, which correspond to different THz frequencies, achieving the expected efficacy of a multi-band wave filter. By sweeping external voltages, the capability of the high-sensitivity THz filter can be modulated from single-band to multi-band filtering by changing graphene's Fermi levels. This hybrid THz wave filter study shows promise for the development of selecting channels in THz and 6G communications.
Article
Materials Science, Multidisciplinary
Kelum Perera, Nilanthi Haputhantrige, Md Sakhawat Hossain Himel, Md Mostafa, Alex Adaka, Elizabeth K. Mann, Oleg D. Lavrentovich, Antal Jakli
Summary: This work presents electrically tunable microlenses based on a polymer-stabilized chiral ferroelectric nematic liquid crystal, which exhibit unique properties and lens deformation performance different from traditional liquid crystal lenses. The technology is of great significance in various application fields.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Multidisciplinary Sciences
Yuan Shen, Ingo Dierking
Summary: Understanding collective motion in biological systems is crucial for the development of autonomous robots and swarm computing. This study introduces an experimental platform that mimics the collective motion of living systems using liquid crystal driven by an external electric field. The platform generates hundreds of artificial particle-like solitonic field configurations, called directrons, which exhibit dynamic behaviors similar to those seen in biological systems.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Hengli Feng, Zuoxin Zhang, Jingyu Zhang, Dongchao Fang, Jincheng Wang, Chang Liu, Tong Wu, Guan Wang, Lehui Wang, Lingling Ran, Yang Gao
Summary: This article proposed a dual broadband terahertz bifunction absorber that can be actively tuned to achieve perfect modulation of absorptance and absorption bandwidth. It also has the advantages of being polarization insensitive and maintaining stable absorption at wide angles of oblique incidence.
Article
Materials Science, Multidisciplinary
Chenrun Feng, Rony Saha, Eva Korblova, David Walba, Samuel N. Sprunt, Antal Jakli
Summary: The paper presents electrical, optical, and electro-optical studies of a ferroelectric nematic LC material doped with commercially available chiral dopants, and finds that chiral mixtures can achieve fast switchable reflection colors at low fields.
ADVANCED OPTICAL MATERIALS
(2021)
Article
Physics, Applied
Yang Liu, Jianbang Zhou, Qi Chang, Ji Liu, Jinzu Ji, Li-Hua Shao
Summary: This study has realized a transparent and electrically tunable wave-absorbing metamaterial for stealth technology and electromagnetic protection. The main part of this material adopts a sandwich structure consisting of two layers of indium tin oxide (ITO) and one layer of glass in between. The wave-absorbing performance of the material can be electronically tunable by changing the applied voltage, and it has a wide effective operating frequency range. The metamaterial also has excellent electromagnetic shielding effectiveness.
APPLIED PHYSICS LETTERS
(2022)
Article
Nanoscience & Nanotechnology
Hao Sun, Yu-Sheng Lin
Summary: This article presents a tunable terahertz metamaterial consisting of double connected semicircle-shaped rings and segregated metallic bars. By manipulating the radius of the rings, the resonances can be red-shifted in both TE and TM polarizations. The device shows polarization-dependent characteristics and can be used for single-, dual-, triple-, and quad-resonance switching as well as high-efficiency environmental sensing applications.
Article
Physics, Fluids & Plasmas
Izabela Sliwa, Pavel V. Maslennikov, Alex V. Zakharov
Summary: This article describes the physical mechanism behind the appearance of traveling and nontraveling distortions in a microsized homogeneously aligned nematic film under the effect of a large electric field. Numerical studies reveal that the director's field may experience a traveling distortion wave in response to the electric field, with the rate of distortion depending on the magnitude of the applied field.
Article
Materials Science, Multidisciplinary
Guangsheng Deng, Hualong Hu, Haisheng Mo, Junjie Xu, Zhiping Yin, Hongbo Lu, Minggang Hu, Jian Li, Jun Yang
Summary: This paper presents a tunable metamaterial absorber based on liquid crystal with wideband absorption, showing excellent performance and applicability for electromagnetic shielding and stealth applications.
OPTICAL MATERIALS EXPRESS
(2021)
Article
Materials Science, Multidisciplinary
Siyuan Liu, Xiaoxing Yin, Hongxin Zhao
Summary: This work presents a photo-excited terahertz metamaterial absorber (PETMA) that can be switched between single-band and narrow-band absorption. The PETMA consists of three layers, including a metal plate, a dielectric layer, and a top unit attached to the dielectric substrate. By controlling the conductivity of silicon using an optical pump beam, the PETMA can achieve single-band and narrow-band absorption at different frequencies. The simulations demonstrate that the proposed PETMA exhibits stable absorption performance at wider incident angles.
RESULTS IN PHYSICS
(2022)
Article
Engineering, Electrical & Electronic
Chuan Shen, Jiali Sun, Yifei Qi, Shiqi Lv, Sui Wei
Summary: This paper presents a method of meta-holographic encryption by integrating liquid crystals with all-dielectric metasurfaces, which can achieve information encryption and decryption in the visible range with high security and flexible adjustment.
IEEE PHOTONICS JOURNAL
(2021)
Article
Optics
Hao Pan, Haifeng Zhang
Summary: In this paper, a thermally tunable ultra-broadband polarization-insensitive terahertz metamaterial absorber (MMA) is proposed, which achieves absorption over a wide band, is insensitive to the polarization angle, and can adjust absorption by tuning the conductivity controlled by temperature.
Article
Polymer Science
Giuseppe Boniello, Victoria Vilchez, Emmanuel Garre, Frederic Mondiot
Summary: Shaping liquid crystals into arrays of defect patterns allows for the design of composite materials with new stimulus-responsive properties. By in situ polymerization of the texture of SmA FCDs, it is possible to transfer them into more electrically responsive LC phases, enabling a dynamic switch between different textural and optical states in a reversible manner with voltage. This approach may lead to new applications of SmA defect patterns and inspire the design of LC-based nanostructured composite materials with new functions that can be dynamically tuned with voltage.
MACROMOLECULAR RAPID COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Amir Maghoul, Ali Rostami, Azeez Abdullah Barzinjy, Peyman Mirtaheri
Summary: A graphene-based perfect terahertz absorber is proposed in this study, with the ability to tune the position of the absorption peak and modulate the intensity and frequency of the absorption peak by varying the Fermi potential. The absorption band can be tuned in the bandwidth from 5 to 15 in terahertz, showing potential for future applications in photodetectors, solar cells, and thermal sensors.
APPLIED SCIENCES-BASEL
(2021)
Article
Multidisciplinary Sciences
Alvin Modin, Biswarup Ash, Kelsey Ishimoto, Robert L. Leheny, Francesca Serra, Hillel Aharoni
Summary: This study introduces a theoretical framework to quantitatively predict the connectivity and shape of disclination lines in liquid crystals. Through experimental testing and computer simulations, it is found that certain parameters can tune the curvature of disclination lines. This research provides a powerful method to understand and control defect lines in liquid crystals.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Physics, Applied
Victor Dmitriev, Dimitrios C. Zografopoulos, Silvio Domingos Silva Santos, Gabriel Felipe da Silva Barros
Summary: We propose and investigate a new all-dielectric flat metasurface based on high-index dielectric disks. The unit cell consists of four disks, which excite quasi-dark toroidal dipole resonances. By breaking the symmetry of the unit cell and the supercell, we can access the toroidal supermodes in the metasurface. Different mechanisms of symmetry reduction are discussed, and the simulations confirm the theoretical predictions. Possible applications of the analyzed structures are also discussed.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Optics
Konstantinos P. Prokopidis, Dimitrios C. Zografopoulos
Summary: This work presents an alternating-direction implicit finite-difference time-domain scheme for the study of structures involving materials with arbitrary frequency dispersion. The proposed technique combines the complex-conjugate pole-residue model with auxiliary differential equations and two-step ADI methodology. It is proven to be robust and capable of simulating applications in different frequency regions. The algorithm provides a powerful tool for the analysis of nanostructures involving strongly dispersive and nanosized materials.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
(2022)
Article
Optics
J. F. Algorri, F. Dell'Olio, P. Roldan-Varona, L. Rodriguez-Cobo, J. M. Lopez-Higuera, J. M. Sanchez-Pena, V Dmitriev, D. C. Zografopoulos
Summary: A silicon metasurface supporting electromagnetically induced transparency (EIT) based on quasi-bound states in the continuum (qBIC) is proposed and demonstrated theoretically, showing sharp high-transmittance peaks within a low-transmittance spectral window. The metasurface, with its high quality factor qBIC resonances, can be used in biosensing applications due to its simple bulk geometry. The proposed metasurface's strong energy confinement and sharp EIT-effect have potential applications in nonlinear devices, lasing, biological sensors, optical trapping, and optical communications.
Article
Optics
N. Bennis, T. Jankowski, P. Morawiak, A. Spadlo, D. C. Zografopoulos, J. M. Sanchez-Pena, J. M. Lopez-Higuera, J. F. Algorri
Summary: In this work, a technique to generate aspherical liquid crystal lenses with positive and negative optical power is experimentally demonstrated. The technique utilizes micro-metric electrode with variable spatial size as the main enabling element. By gradually decreasing resistance and uniformly distributing voltage, the desired phase profiles are achieved, resulting in parabolic profiles for both positive and negative optical powers.
Article
Optics
Mohsen Samadi, Fatemeh Abshari, Jose F. Algorri, Pablo Roldan-Varona, Luis Rodriguez-Cobo, Jose M. Lopez-Higuera, Jose M. Sanchez-Pena, Dimitrios C. Zografopoulos, Francesco Dell'Olio
Summary: All-dielectric metasurfaces are of great research interest due to their lower losses and sharper resonances. This study presents an all-dielectric silicon metasurface based on CSRRs optimized for refractive index sensing, achieving an ultra-high performance sensor using quasi-BIC resonance.
Article
Physics, Applied
Walter Fuscaldo, Sara De Simone, Dimitre Dimitrov, Vera Marinova, Valentina Mussi, Romeo Beccherelli, Dimitrios C. Zografopoulos
Summary: This research presents a method for characterizing the THz conductivity of graphene on metal-backed substrates and validates its effectiveness through experiments. This method allows for rapid and accurate nondestructive characterization of graphene sheets, which can be integrated into the production of components such as THz absorbers, lenses, and antennas.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Engineering, Electrical & Electronic
Dimitrios Chatzidimitriou, Dimitrios C. Zografopoulos, Emmanouil E. Kriezis
Summary: This study demonstrates the theoretical application of graphene saturable absorption for saturable absorption mirrors based on planar silicon photonic Bragg gratings. Two geometries, silicon wire grating and silicon slot grating, were investigated to showcase the enhanced interaction between light and matter in high-confinement slot waveguides. The effects of other nonlinear properties, such as silicon's Kerr effect and two photon absorption, were also considered but were shown to have a negligible impact compared to graphene's saturable absorption.
IEEE PHOTONICS JOURNAL
(2022)
Article
Multidisciplinary Sciences
D. C. Zografopoulos, J. F. Algorri, J. M. Lopez-Higuera, H. E. Hernandez-Figueroa, V Dmitriev
Summary: This study investigates quasi-dark resonances with antiferromagnetic order in a near-infrared metasurface. By reducing the symmetry of the metasurface, access to the quasi-dark mode is achieved. The study reveals the key optical properties of the quasi-dark mode, including resonant wavelengths, quality factors, and angular dispersion. The thickness of the silicon metasurface and the angle of incidence can be used to adjust the asymmetry degree and resonant wavelength of the mode.
SCIENTIFIC REPORTS
(2022)
Article
Multidisciplinary Sciences
Victor Dmitriev, Dimitrios C. C. Zografopoulos, Luis P. V. Matos
Summary: We discuss a method based on magnetic group theory for analyzing symmetric electromagnetic components with magnetic media. In this method, some of the irreducible corepresentations take on complex values exp(i theta), where theta is a real parameter. We provide a possible physical interpretation for this parameter. The symmetry-adapted linear combination method combined with the corepresentation theory is applied to the problem of current modes in an array of magnetized graphene elements. Numerical simulations and analyses are presented for the scattering matrix and eigensolutions of the array, as well as an example of a waveguide with a specific type of degeneracy described by symmetry C(4)v(C(2)v).
Article
Optics
J. F. Algorri, F. Dell'Olio, Y. Ding, F. Labbe, V. Dmitriev, J. M. Lopez-Higuera, J. M. Sanchez-Pena, L. C. Andreani, M. Galli, D. C. Zografopoulos
Summary: We investigate a metasurface supporting a silicon-slot quasi-bound state in the continuum (qBIC) mode resonating in the near-infrared spectrum both theoretically and experimentally. The metasurface is composed of circular slots etched in a silicon layer on a sapphire substrate. By reducing the symmetry of the metasurface unit cell, we access the symmetry-protected mode and analyze its properties through finite-element full-wave and eigenfrequency analysis. The measured transmittance spectra confirm the excitation of the investigated qBIC mode with experimental quality factors exceeding 700. The resonant qBIC mode exhibits strong field confinement in the slots, leading to high sensitivity values for refractometry.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Chemistry, Analytical
Odysseas Tsilipakos, Zacharias Viskadourakis, Anna C. Tasolamprou, Dimitrios C. Zografopoulos, Maria Kafesaki, George Kenanakis, Eleftherios N. Economou
Summary: A conductive meta-atom of toroidal topology is studied for its sharp and highly controllable resonant response. The structure is fabricated with 3D printing and coated with silver paste, resulting in a practical and potentially low-loss system. Measurements show good agreement with simulations in the 5 GHz regime.
Article
Chemistry, Multidisciplinary
Jose Francisco Algorri, Victor Dmitriev, Jose Miguel Lopez-Higuera, Dimitrios C. Zografopoulos
Summary: This study proposes a novel dielectric metasurface that addresses the two main problems in sensing and spectroscopy based on electromagnetic field enhancement. By supporting delocalized modes and quasi-bound states in the continuum, the metasurface achieves polarization-insensitive, high-Q-factor resonances with very high electric field enhancements. This work opens up new research opportunities in optical sensing and advanced spectroscopy.
Article
Computer Science, Information Systems
Walter Fuscaldo, Elahehsadat Torabi, Dimitrios C. Zografopoulos, Danilo Erricolo, Romeo Beccherelli
Summary: This paper proposes a rectangular metallic leaky waveguide antenna loaded with liquid crystals to mitigate the trade-off between directivity and tunable angular range in dynamic beamscanning antennas. The antenna design is optimized to achieve a tunable angular range of 28 degrees while maintaining a gain of 7 dBi. Rigorous modeling and full-wave simulations validate the antenna's performance.
Review
Materials Science, Multidisciplinary
Dimitrios C. Zografopoulos, Odysseas Tsilipakos
Summary: All-dielectric metasurfaces have been extensively studied as a flat-optics platform for advanced manipulation of electromagnetic waves. They can be engineered to have either extremely narrowband response or ultrabroadband response, opening the path towards enhanced light-matter interaction and strong field enhancement, or achromatic, flat components for imaging and ultra-short pulse processing applications.
MATERIALS ADVANCES
(2023)
Proceedings Paper
Optics
Mohsen Samadi, Fatemeh Abshari, J. F. Algorri, P. Roldan-Varona, L. Rodriguez-Cobo, J. M. Lopez-Higuera, J. M. Sanchez-Pena, D. C. Zografopoulos, F. Dell'Olio
Summary: In this study, we numerically investigated the optical performance of a novel all-dielectric metasurface based on CSRRs, showing dual-polar resonances in the NIR window and the excitation of a quasi-BIC with ultra-high quality factor by breaking the symmetry of the structure. By utilizing these characteristics, an ultra-high figure of merit refractive index sensor was designed for biomedical applications.
LASER RESONATORS, MICRORESONATORS, AND BEAM CONTROL XXIV
(2022)
