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Metasurfaces for Photonic Devices: Theory and Applications
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Metasurfaces for Photonic Devices: Theory and Applications

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanophotonics Materials and Devices".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 33227

Special Issue Editors

Dr. Weiren Zhu

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Guest Editor
Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Interests: metamaterials; metasurfaces
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Fajun Xiao

E-Mail Website
Guest Editor
Key Laboratory of Light Field Manipulation and Information Acquisition, Ministry of Industry and Information Technology and Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern Polytechnical University, Xi’an 710129, China
Interests: plasmonic; spatial structured light; nonlinear optics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The advancement of modern electromagnetic technologies relies on the development of original theoretical approaches and new artificial materials. Artificially structured composites, known as metamaterials, exhibit novel properties that do not exist in natural materials, broadening human abilities in manipulating electromagnetic waves. Metamaterials provide a unique pathway to generate, guide, modulate, and detect electromagnetic waves by having structural features that are significantly smaller than the operation wavelength. The development of metamaterials enables intriguing applications ranging from wavefront manipulation, imaging at subwavelength resolution, invisibility cloaks, new concept antennas, data processing, and highly flexible sensing and modulation, which have been receiving significant attention among both the scientific and engineering communities.

The proposed Special Issue aims to offer a collection of the recent developments in electromagnetic metamaterials, metasurfaces, and surface plasmonics and explore their potential usefulness in various aspects, both experimentally and theoretically. We hope this Special Issue could stimulate continuing efforts on the understanding of electromagnetic metamaterials and exploring their applications. Tremendous efforts are still ongoing in this fascinating area. We expect that more and more new real applications of metamaterials and meta-devices will become a reality in the near future.

Original research articles and reviews are welcome for submission in this Special Issue. Research areas of interest include (but are not limited to) the following:

  • Novel designs for metamaterials/metasurfaces;
  • Microphotonics, nanophotonics, plasmonics, and novel optical devices;
  • Optical imaging and sensing;
  • Plasmon-enhanced light–matter interaction at the nanoscale;
  • Graphene metamaterials and devices;
  • Metamaterials/metasurfaces for antennas and RF devices.

Prof. Dr. Weiren Zhu
Prof. Dr. Fajun Xiao
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Metamaterials
  • Metasurfaces
  • Nanophotonics
  • Plasmonics

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Published Papers (17 papers)

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11 pages, 6504 KiB  
Article
Precision Tailoring Quasi-BIC Resonance of a-Si:H Metasurfaces
by Athira Kuppadakkath, Ángela Barreda, Lilit Ghazaryan, Tobias Bucher, Kirill Koshelev, Thomas Pertsch, Adriana Szeghalmi, Duk Choi, Isabelle Staude and Falk Eilenberger
Nanomaterials 2023, 13(11), 1810; https://doi.org/10.3390/nano13111810 - 5 Jun 2023
Cited by 3 | Viewed by 1738
Abstract
The capability of tailoring the resonance wavelength of metasurfaces is important as it can alleviate the manufacturing precision required to produce the exact structure according to the design of the nanoresonators. Tuning of Fano resonances by applying heat has been theoretically predicted in [...] Read more.
The capability of tailoring the resonance wavelength of metasurfaces is important as it can alleviate the manufacturing precision required to produce the exact structure according to the design of the nanoresonators. Tuning of Fano resonances by applying heat has been theoretically predicted in the case of silicon metasurfaces. Here, we experimentally demonstrate the permanent tailoring of quasi-bound states in the continuum (quasi-BIC) resonance wavelength in an a-Si:H metasurface and quantitatively analyze the modification in the Q-factor with gradual heating. A gradual increment in temperature leads to a spectral shift in the resonance wavelength. With the support of ellipsometry measurements, the spectral shift resulting from the short-duration (ten minutes) heating is identified to be due to refractive index variations in the material rather than a geometric effect or amorphous/polycrystalline phase transition. In the case of quasi-BIC modes in the near-infrared, resonance wavelength could be adjusted from T = 350 °C to T = 550 °C without affecting the Q-factor considerably. Apart from the temperature-induced resonance trimming, large Q-factors can be attained at the highest analyzed temperature (T = 700 °C) in the near-infrared quasi-BIC modes. Resonance tailoring is just one of the possible applications of our results. We expect that our study is also insightful in the design of a-Si:H metasurfaces where large Q-factors are required at high temperatures. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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11 pages, 9207 KiB  
Article
Three-Channel Near-Field Display and Encryption Based on a Polarization Multiplexed Metasurface
by Jiadong Yuan, Zuyu Li, Yuhan Hong, Yuhang Zhang, Hongzhan Liu and Zhongchao Wei
Nanomaterials 2023, 13(10), 1638; https://doi.org/10.3390/nano13101638 - 14 May 2023
Viewed by 1314
Abstract
Multichannel metasurfaces are becoming a significant trend in the field of optical encryption due to their excellent manipulation of optical wavefronts. However, existent multichannel metasurfaces for optical encryption mostly implement only two channels in the near-field, or three channels by combining the near- [...] Read more.
Multichannel metasurfaces are becoming a significant trend in the field of optical encryption due to their excellent manipulation of optical wavefronts. However, existent multichannel metasurfaces for optical encryption mostly implement only two channels in the near-field, or three channels by combining the near- and far-field. In this paper, we propose and simulate a three-channel metasurface that works entirely in the near-field and uses the polarization state of the incident light, left circularly polarized (LCP) light, right circularly polarized (RCP) light, and linearly polarized (LP) light as the security key. The metasurface consists of two types of nanostructures that work as a polarizer and a quarter-wave plate, providing an additional degree of freedom for encoding that enables independent near-field display at 633 nm wavelength incident light. The proposed three-channel metasurface has the advantages of high information density and high security, which will pave the way for multi-channel applications such as ultracompact displays, optical encryption, and information storage. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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14 pages, 2310 KiB  
Article
Polarization-Dependent Metasurface Enables Near-Infrared Dual-Modal Single-Pixel Sensing
by Rong Yan, Wenli Wang, Yao Hu, Qun Hao and Liheng Bian
Nanomaterials 2023, 13(9), 1542; https://doi.org/10.3390/nano13091542 - 4 May 2023
Cited by 1 | Viewed by 1395
Abstract
Infrared single-pixel sensing with the two most representative modes, bright-field imaging and edge-enhanced imaging, has great application potential in biomedical diagnosis and defect inspection. Building a multifunctional and miniature optical computing device for infrared single-pixel sensing is extremely intriguing. Here, we propose and [...] Read more.
Infrared single-pixel sensing with the two most representative modes, bright-field imaging and edge-enhanced imaging, has great application potential in biomedical diagnosis and defect inspection. Building a multifunctional and miniature optical computing device for infrared single-pixel sensing is extremely intriguing. Here, we propose and validate a dual-modal device based on a well-designed metasurface, which enables near-infrared bright-field and edge-enhanced single-pixel imaging. By changing the polarization of the incident beam, these two different modes can be switched. Simulations validate that our device can achieve high-fidelity dual-modal single-pixel sensing at 0.9 μm with certain noise robustness. We also investigate the generalization of our metasurface-based device and validate that different illumination patterns are applied to our device. Moreover, these output images by our device can be efficiently utilized for biomedical image segmentation. We envision this novel device may open a vista in dual-modal infrared single-pixel sensing. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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9 pages, 1813 KiB  
Article
Bionic Plasmonic Nanoarrays Excited by Radially Polarized Vector Beam for Metal-Enhanced Fluorescence
by Min Liu, Lan Yu, Yanru Li, Ying Ma, Sha An, Juanjuan Zheng, Lixin Liu, Ke Lin and Peng Gao
Nanomaterials 2023, 13(7), 1237; https://doi.org/10.3390/nano13071237 - 31 Mar 2023
Viewed by 1142
Abstract
Metal-enhanced fluorescence (MEF) is an important fluorescence technology due to its ability to significantly improve the fluorescence intensity. Here, we present a new MEF configuration of the bionic nanorod array illuminated by radially polarized vector beam (RVB). The bionic nanorod array is fabricated [...] Read more.
Metal-enhanced fluorescence (MEF) is an important fluorescence technology due to its ability to significantly improve the fluorescence intensity. Here, we present a new MEF configuration of the bionic nanorod array illuminated by radially polarized vector beam (RVB). The bionic nanorod array is fabricated via a nanoimprinting method by using the wings of the Chinese cicada “meimuna mongolica” as bio-templates, and later coating gold film by ion sputtering deposition method. The MEF performance of the prepared substrate is tested by a home-made optical system. The experiment results show that, in the case of RVB excitation, the intensity of fluorescence is more than 10 times stronger with the nano-imprinted substrate than that with glass. Using the bionic nanoarray as a substrate, the intensity of fluorescence is ~2 times stronger via RVB than that by the linearly polarized beam. In addition, the prepared substrate is verified to have good uniformity. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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13 pages, 1412 KiB  
Article
Lightweight Machine-Learning Model for Efficient Design of Graphene-Based Microwave Metasurfaces for Versatile Absorption Performance
by Nengfu Chen, Chong He and Weiren Zhu
Nanomaterials 2023, 13(2), 329; https://doi.org/10.3390/nano13020329 - 12 Jan 2023
Cited by 3 | Viewed by 1961
Abstract
Graphene, as a widely used nanomaterial, has shown great flexibility in designing optically transparent microwave metasurfaces with broadband absorption. However, the design of graphene-based microwave metasurfaces relies on cumbersome parameter sweeping as well as the expertise of researchers. In this paper, we propose [...] Read more.
Graphene, as a widely used nanomaterial, has shown great flexibility in designing optically transparent microwave metasurfaces with broadband absorption. However, the design of graphene-based microwave metasurfaces relies on cumbersome parameter sweeping as well as the expertise of researchers. In this paper, we propose a machine-learning network which enables the forward prediction of reflection spectra and inverse design of versatile microwave absorbers. Techniques such as the normalization of input and transposed convolution layers are introduced in the machine-learning network to make the model lightweight and efficient. Particularly, the tunable conductivity of graphene enables a new degree in the intelligent design of metasurfaces. The inverse design system based on the optimization method is proposed for the versatile design of microwave absorbers. Representative cases are demonstrated, showing very promising performances on satisfying various absorption requirements. The proposed machine-learning network has significant potential for the intelligent design of graphene-based metasurfaces for various microwave applications. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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13 pages, 4657 KiB  
Article
Three-Channel Metasurfaces for Multi-Wavelength Holography and Nanoprinting
by Zuyu Li, Yuhang Zhang, Jiadong Yuan, Yuhan Hong, Hongzhan Liu, Jianping Guo, Qiaofeng Dai and Zhongchao Wei
Nanomaterials 2023, 13(1), 183; https://doi.org/10.3390/nano13010183 - 31 Dec 2022
Cited by 7 | Viewed by 1635
Abstract
Metasurfaces, employed to simultaneously generate nanoprinting and holographic images, have been extensively explored recently. Among them, multi-wavelength multiplexing in a single metasurface is often accompanied by dispersion and crosstalk, which hinder the display of multicolor patterns. Here, we propose an efficient phase method [...] Read more.
Metasurfaces, employed to simultaneously generate nanoprinting and holographic images, have been extensively explored recently. Among them, multi-wavelength multiplexing in a single metasurface is often accompanied by dispersion and crosstalk, which hinder the display of multicolor patterns. Here, we propose an efficient phase method to decouple the wavelength and realize a three-channel display operating at different wavelengths. Holographic images appear in the far field with the illumination of two different circularly polarized lights while a nanoprinting image is reconstructed by inserting an orthogonal optical path with the illumination of linear polarization light. The proposed metasurface is only composed of four types of unit cells, which significantly decreases the complexity of fabrication and improves the information capacity. Benefiting from its different decoding strategies and capability of multi-wavelength control, this approach may develop broad applications in information encryption, security, and color display. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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11 pages, 3369 KiB  
Article
Tunable Light Field Modulations with Chip- and Fiber-Compatible Monolithic Dielectric Metasurfaces
by Bobo Du, Yunfan Xu, Huimin Ding, Weitao Jiang, Lei Zhang and Yanpeng Zhang
Nanomaterials 2023, 13(1), 69; https://doi.org/10.3390/nano13010069 - 23 Dec 2022
Cited by 1 | Viewed by 2092
Abstract
Metasurfaces with a high engineering degree of freedom are promising building blocks for applications in metalenses, beam deflectors, metaholograms, sensing, and many others. Though the fundamental and technological challenges, proposing tunable metasurfaces is still possible. Previous efforts in this field are mainly taken [...] Read more.
Metasurfaces with a high engineering degree of freedom are promising building blocks for applications in metalenses, beam deflectors, metaholograms, sensing, and many others. Though the fundamental and technological challenges, proposing tunable metasurfaces is still possible. Previous efforts in this field are mainly taken on designing sophisticated structures with active materials introduced. Here, we present a generic kind of monolithic dielectric metasurfaces for tunable light field modulations. Changes in the period number and surrounding refractive index enable discrete and continuous modulations of spatial light fields, respectively. We exemplify this concept in monolithic Lithium Niobate metasurfaces for tunable metalenses and beam deflectors. The utilization of monolithic dielectric materials facilitates the ready integration of the metasurfaces with both chip and optical fiber platforms. This concept is not limited by the availability of active materials or expensive and time-consuming fabrication techniques, which can be applied to any transparent dielectric materials and various optical platforms. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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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 1337
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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12 pages, 3403 KiB  
Article
Multifield-Controlled Terahertz Hybrid Metasurface for Switches and Logic Operations
by Xilai Zhao, Yanan Jiao, Jiangang Liang, Jing Lou, Jing Zhang, Jiawen Lv, Xiaohui Du, Lian Shen, Bin Zheng and Tong Cai
Nanomaterials 2022, 12(21), 3765; https://doi.org/10.3390/nano12213765 - 26 Oct 2022
Cited by 3 | Viewed by 1838
Abstract
Terahertz (THz) meta-devices are considered to be a promising framework for constructing integrated photonic circuitry, which is significant for processing the upsurge of data brought about by next-generation telecommunications. However, present active metasurfaces are typically restricted by a single external driving field, a [...] Read more.
Terahertz (THz) meta-devices are considered to be a promising framework for constructing integrated photonic circuitry, which is significant for processing the upsurge of data brought about by next-generation telecommunications. However, present active metasurfaces are typically restricted by a single external driving field, a single modulated frequency, fixed switching speed, and deficiency in logical operation functions which prevents devices from further practical applications. Here, to overcome these limitations, we propose a hybrid THz metasurface consisting of vanadium dioxide (VO2) and germanium (Ge) that enables electrical and optical tuning methods individually or simultaneously and theoretically investigate its performance. Each of the two materials is arranged in the meta-atom to dominate the resonance strength of toroidal or magnetic dipoles. Controlled by either or both of the external excitations, the device can switch on or off at four different frequencies, possessing two temporal degrees of freedom in terms of manipulation when considering the nonvolatility of VO2 and ultrafast photogenerated carriers of Ge. Furthermore, the “AND” and “OR” logic operations are respectively achieved at two adjacent frequency bands by weighing normalized transmission amplitude. This work may provide an auspicious paradigm of THz components, such as dynamic filters, multiband switches, and logical modulators, potentially promoting the design and implementation of multifunctional electro-optical devices in future THz computing and communication. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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8 pages, 2028 KiB  
Article
Dielectric Metalens for Superoscillatory Focusing Based on High-Order Angular Bessel Function
by Yu Li, Xinhao Fan, Yunfeng Huang, Xuyue Guo, Liang Zhou, Peng Li and Jianlin Zhao
Nanomaterials 2022, 12(19), 3485; https://doi.org/10.3390/nano12193485 - 5 Oct 2022
Cited by 2 | Viewed by 1527
Abstract
The phenomenon of optical superoscillation provides an unprecedented way to solve the problem of optical far-field label-free super-resolution imaging. Numerous optical devices that enable superoscillatory focusing were developed based on scalar and vector diffraction theories in the past several years. However, these reported [...] Read more.
The phenomenon of optical superoscillation provides an unprecedented way to solve the problem of optical far-field label-free super-resolution imaging. Numerous optical devices that enable superoscillatory focusing were developed based on scalar and vector diffraction theories in the past several years. However, these reported devices are designed according to the half-wave zone method in spatial coordinates. In this paper, we propose a dielectric metalens for superoscillatory focusing based on the diffraction of angular Bessel functional phase modulated vector field, under the inspiration of the tightly autofocusing property of a radially polarized high-order Bessel beam. Based on this kind of metalens with a numerical aperture (NA) of 0.9, the linearly polarized light is converted into a radially polarized one and then focus into a superoscillating focal spot with the size of 0.32λ/NA. This angular spectrum modulation theory involved in this paper provides a different way of designing superoscillatory devices. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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11 pages, 3032 KiB  
Article
Multi-Band High-Efficiency Multi-Functional Polarization Controller Based on Terahertz Metasurface
by Huaijun Chen, Wenxia Zhao, Xuejian Gong, Lianlian Du, Yunshan Cao, Shilong Zhai and Kun Song
Nanomaterials 2022, 12(18), 3189; https://doi.org/10.3390/nano12183189 - 14 Sep 2022
Cited by 9 | Viewed by 1886
Abstract
Electromagnetic metasurfaces with excellent electromagnetic wave regulation properties are promising for designing high-performance polarization control devices, while the application prospect of electromagnetic metasurfaces is limited because of the current development situations of the complex structure, low conversion efficiency, and narrow working bandwidth. In [...] Read more.
Electromagnetic metasurfaces with excellent electromagnetic wave regulation properties are promising for designing high-performance polarization control devices, while the application prospect of electromagnetic metasurfaces is limited because of the current development situations of the complex structure, low conversion efficiency, and narrow working bandwidth. In this work, we design a type of reflective terahertz metasurface made of a simple structure that can achieve multiple polarization modulation with high efficiency. It is shown that the presented metasurface can realize ultra-broadband, cross-polarization conversion with the relative working bandwidth reaching 94% and a conversion efficiency of over 90%. In addition, the proposed metasurface can also efficiently accomplish different polarization conversion functions, such as linear-to-linear, linear-to-circular, or circular-to-linear polarization conversion in multiple frequency bands. Due to the excellent properties, the designed metasurface can be used as a high-efficiency multi-functional polarization modulation device, and it has important application value in terahertz imaging, communication, biological detection, and other fields. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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7 pages, 1705 KiB  
Article
Field Enhancement for the Composite MXene/Black Phosphorus-Based Metasurface
by Yihui Zhou, Lingqiao Li, Zhihui He, Yixuan Wang, Wei Cui, Zhimin Yang, Shaojun Lu, Xiongxiong Wu and Lang Bai
Nanomaterials 2022, 12(18), 3155; https://doi.org/10.3390/nano12183155 - 11 Sep 2022
Cited by 3 | Viewed by 1549
Abstract
Both MXene and black phosphorus (BP), which actg as hot two-dimensional (2D) materials, have unique optical properties and important applications for nano-micro optical devices. Here, a composite MXene/BP-based metasurface, consisting of Ti3C2Tx and BP layers, is proposed for [...] Read more.
Both MXene and black phosphorus (BP), which actg as hot two-dimensional (2D) materials, have unique optical properties and important applications for nano-micro optical devices. Here, a composite MXene/BP-based metasurface, consisting of Ti3C2Tx and BP layers, is proposed for investigating the optical responses and electric field by using the finite-difference time-domain numerical simulation method in the microwave band. The research results show that the Fano resonance-like spectra can be observed when the coupling of surface plasmons (SPs) on the BP and MXene layers appears. Furthermore, the field enhancement, based on the Fano resonance-like optical responses, can be improved by an order of magnitude through adjusting the structural parameters and the polarization direction of incident light for the proposed metasurface. The findings may provide important theoretical insights into the design and realization of high-performance plasmonic devices. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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14 pages, 4499 KiB  
Article
Circularly Polarized Antenna Array with Decoupled Quad Vortex Beams
by Shuo Xu, He-Xiu Xu, Yanzhao Wang, Jian Xu, Chaohui Wang, Zhichao Pang and Huiling Luo
Nanomaterials 2022, 12(17), 3083; https://doi.org/10.3390/nano12173083 - 5 Sep 2022
Cited by 3 | Viewed by 1633
Abstract
Achieving multiple vortex beams with different modes in a planar microstrip array is pivotal, yet still extremely challenging. Here, a hybrid method combining both Pancharatnam−Berry (PB) phase that is induced by the rotation phase and excitation phase of a feeding line has been [...] Read more.
Achieving multiple vortex beams with different modes in a planar microstrip array is pivotal, yet still extremely challenging. Here, a hybrid method combining both Pancharatnam−Berry (PB) phase that is induced by the rotation phase and excitation phase of a feeding line has been proposed for decoupling two orthogonal circularly polarized vortex beams. Theoretical analysis is derived for array design to generate quad vortex beams with different directions and an arbitrary number of topological charges. On this basis, two 8 × 8 planar arrays were theoretically designed in an X band, which are with topological charges of l1 = −1, l2 = 1, l3 = −1, and l4 = 1 in Case I and topological charges of l1 = −1, l2 = 1, l3 = −1, and l4 = 1 in Case II. To further verify the above theory, the planar array in Case I is fabricated and analyzed experimentally. Dual-LP beams are realized by using rectangular patch elements with two orthogonally distributed feeding networks on different layers based on two types of feeding: proximity coupling and aperture coupling. Both the numerical simulation and experimental measurement results are in good agreement and showcase the corresponding quad-vortex-beam characteristics within 8~12 GHz. The array achieves a measured S11 < −10 dB and S22 < −10 dB bandwidth of more than 33.4% and 29.2%, respectively. In addition, the isolation between two ports is better than −28 dB. Our strategy provides a promising way to achieve large capacity and high integration, which is of great benefit to wireless and radar communication systems. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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10 pages, 3578 KiB  
Article
Ultra-Thin, Short-Focus, and High-Aperture Metalens for Generating and Detecting Laser Optical Vortices
by Anton Nalimov and Victor Kotlyar
Nanomaterials 2022, 12(15), 2602; https://doi.org/10.3390/nano12152602 - 28 Jul 2022
Cited by 8 | Viewed by 1581
Abstract
A combined high-aperture metalens in a thin silicon nitride film that consists of two tilted sectored metalenses is considered. Each sector of the metalens consists of a set of binary subwavelength gratings. The diameter of the metalens is 14 μm. Using a time-domain [...] Read more.
A combined high-aperture metalens in a thin silicon nitride film that consists of two tilted sectored metalenses is considered. Each sector of the metalens consists of a set of binary subwavelength gratings. The diameter of the metalens is 14 μm. Using a time-domain finite difference method, we show that the metalens can simultaneously detect optical vortices with two topological charges −1 and −2, almost over the entire spectrum of visible wavelengths. The metalens can distinguish several wavelengths that are focused at different points in the focal plane due to a 1-nm change in wavelength resulting in a focal spot shift of about 4 nm. When the metalens is illuminated by a Gaussian beam with left-handed circular polarization, two optical vortices with topological charges 1 and 2 are simultaneously formed 6-μm apart at the focal distance of 6 μm. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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12 pages, 4494 KiB  
Article
Design of Multifunctional Tunable Metasurface Assisted by Elastic Substrate
by Jing Li, Hongjie Fan, Han Ye, Tiesheng Wu, Yuhang Sun, Xueyu Wang and Yumin Liu
Nanomaterials 2022, 12(14), 2387; https://doi.org/10.3390/nano12142387 - 13 Jul 2022
Cited by 9 | Viewed by 1728
Abstract
Metasurfaces with both multifunctionality and tunability hold great application potential in next-generation optical devices. In this paper, we propose a stretchable metasurface composed of arrays of identical dielectric rectangular resonators embedded in the polydimethylsiloxane (PDMS) substrate. It is shown that the metasurface possesses [...] Read more.
Metasurfaces with both multifunctionality and tunability hold great application potential in next-generation optical devices. In this paper, we propose a stretchable metasurface composed of arrays of identical dielectric rectangular resonators embedded in the polydimethylsiloxane (PDMS) substrate. It is shown that the metasurface possesses three functions at the operating wavelength of 532 nm. The switching of functions can be implemented by changing the period Px of the metasurface, induced by stretching the PDMS substrate along the x-direction. When the period Px is less than the operating wavelength of 532 nm, the behavior of metasurface can switch between transmissive window and reflective mirror. When the period Px of the metasurface varies from 532 nm to 700 nm, the metasurface act as a dynamic equal-power beam splitter with conversion efficiency higher than 90%, and the corresponding splitting angle can be adjusted from 90° to around 49.5°. Moreover, we achieve the switching of transmissive window/reflective mirror/split-ratio-variable splitter based on the metasurface consisting of arrays of identical L-shaped resonators embedded in the PDMS substrate. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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9 pages, 3201 KiB  
Article
A Photoexcited Switchable Dual-Function Metamaterial Absorber for Sensing and Wideband Absorption at THz Band
by Liansheng Wang, Dongyan Xia, Quanhong Fu, Yuan Wang and Xueyong Ding
Nanomaterials 2022, 12(14), 2375; https://doi.org/10.3390/nano12142375 - 11 Jul 2022
Cited by 1 | Viewed by 1461
Abstract
Based on the tunable conductivity of silicon as a function of incident pump power, a photoexcited switchable dual-function metamaterial absorber for sensing and wideband absorption at the THz band is designed in this paper. The absorber has an absorption peak at 2.08 THz [...] Read more.
Based on the tunable conductivity of silicon as a function of incident pump power, a photoexcited switchable dual-function metamaterial absorber for sensing and wideband absorption at the THz band is designed in this paper. The absorber has an absorption peak at 2.08 THz with the absorption up to 99.6% when the conductivity of silicon is 150 Sm−1, which can be used for sensing. The refractive index sensitivity of the absorption peak is up to 456 GHz/RIU. A wideband absorption is generated from 3.4 THz to 4.5 THz with the bandwidth of 1.1 THz as the conductivity σsi = 12,000 Sm−1. The generation mechanism of the sensing absorption peak and wideband absorption is explained by monitoring the surface current, electric, and magnetic field distribution at some absorption frequencies. It has the advantages of being simple and having a high sensitivity, and wideband absorption with wide application prospects on terahertz communication, electromagnetic stealth, and biochemical detection. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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Review

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27 pages, 4583 KiB  
Review
Recent Advances in Tunable Metasurfaces and Their Application in Optics
by Alberto Santonocito, Barbara Patrizi and Guido Toci
Nanomaterials 2023, 13(10), 1633; https://doi.org/10.3390/nano13101633 - 13 May 2023
Cited by 6 | Viewed by 6024
Abstract
Metasurfaces can be opportunely and specifically designed to manipulate electromagnetic wavefronts. In recent years, a large variety of metasurface-based optical devices such as planar lenses, beam deflectors, polarization converters, and so on have been designed and fabricated. Of particular interest are tunable metasurfaces, [...] Read more.
Metasurfaces can be opportunely and specifically designed to manipulate electromagnetic wavefronts. In recent years, a large variety of metasurface-based optical devices such as planar lenses, beam deflectors, polarization converters, and so on have been designed and fabricated. Of particular interest are tunable metasurfaces, which allow the modulation of the optical response of a metasurface; for instance, the variation in the focal length of a converging metalens. Response tunability can be achieved through external sources that modify the permittivity of the materials constituting the nanoatoms, the substrate, or both. The modulation sources can be classified into electromagnetic fields, thermal sources, mechanical stressors, and electrical bias. Beside this, we will consider optical modulation and multiple approach tuning strategies. A great variety of tunable materials have been used in metasurface engineering, such as transparent conductive oxides, ferroelectrics, phase change materials, liquid crystals, and semiconductors. The possibility of tuning the optical properties of these metamaterials is very important for several applications spanning from basic optics to applied optics for communications, depth sensing, holographic displays, and biochemical sensors. In this review, we summarize the recent progress on electro-optical magnetic, mechanical, and thermal tuning of metasurfaces actually fabricated and experimentally tested in recent years. At the end of the review, a short section on possible future perspectives and applications is included. Full article
(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)
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