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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Metagratings for Efficient Wavefront Manipulation
摘要： Metagratings are two-dimensional periodic arrays of individual scatterers that enable highly-efficient extreme wave transformation which was impossible using conventional metasurfaces. We review our recent progress in this area and, notably, discuss metagrating designs based on asymmetric electric dipoles that are practically easier to realize compared to bianisotropic inclusions. In addition, we present the design of a tunable metagrating based on graphene strips. It will be shown that the proposed structure can provide multiple functionalities by tuning just two bias voltages. The efficiency of the proposed design is only limited by dissipation in graphene.
关键词： wavefront manipulation,Metagratings,graphene strips,asymmetric electric dipoles,tunable metagrating
更新于2025-09-23 15:21:01
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Silicona??Waveguidea??Integrated Higha??Quality Metagrating Supporting Bound State in the Continuum
摘要： The photonic bound state in the continuum (BIC) is a spatially bounded eigen state that can be realized in the form of a supercavity mode with an ultrahigh quality factor. The high-quality supercavity resonance can be supported by photonic crystal slabs, asymmetric metasurfaces, and high-contrast gratings. However, these schemes all suffer from bulky device size and complex experimental setup. Herein, a silicon-waveguide-integrated high-quality metagrating is proposed and demonstrated as a new platform to manipulate the supercavity mode. The shallow-ridge metagrating is directly embedded in the silicon slab waveguide, so the input slab mode can be coupled into the resonant ridge mode, which can be further transformed into the supercavity mode by utilizing the intra-waveguide Fabry–Perot interference. Such an effect has been experimentally verified by the fabricated devices. The metagrating operating near the supercavity regime is also experimentally realized with a high quality factor ≈5200. As an application, such high-quality metagrating is exploited to realize the temperature sensing with a high temperature sensitivity ≈77 pm K?1. The proposed integrated metagrating provides a novel approach to harness the BIC, paving ways for a new class of BIC-based nanophotonic devices with high performance, chip-scale footprint, and long-term stability.
关键词： waveguides,bound state in the continuum,silicon photonics,metagrating
更新于2025-09-23 15:19:57
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[IEEE 2019 International Conference on Electromagnetics in Advanced Applications (ICEAA) - Granada, Spain (2019.9.9-2019.9.13)] 2019 International Conference on Electromagnetics in Advanced Applications (ICEAA) - Exploiting the Properties of Metagratings for Designing Rectangular Waveguide Mode Converters
摘要： We explore the potential of metagrating for designing rectangular waveguide (RWG) TE10-to-TE20 mode converters via detailed analytical modelling. Such converters find their significance in applications like power combiners [1] and mode division multiplexers. Metagratings, on the other hand, are periodic arrays of polarizable particles (meta-atoms), capable of maneuvering electromagnetic wavefronts efficiently for advanced beam manipulation applications, such as beam splitting, and anomalous reflection and refraction [2-3]. This is achieved by tailoring the configuration’s degree of freedom such that energy is funneled exclusively to the desirable Floquet-Bloch (FB) modes, while quenching undesired FB channels by destructive interference. In this paper, we harness this physical mechanism to implement perfect mode coupling in a different electromagnetic system, namely, RWGs. The layout of the proposed configuration is depicted in Fig. 1(a) comprised of a capacitively loaded thin conducting wire placed at a position (x0, z0) in front of a perfect electric conductor (PEC) termination; TE10 mode is driven from the input port to excite the enclosed wire. In order to couple the incident TE10 mode into TE20 mode with unitary efficiency we need to fulfil two conditions: first, elimination of back reflected TE10 mode from the PEC via interference with the corresponding first order FB mode of the excited conducting wire; second, the net real power crossing any plane (z >z0) in the waveguide must be zero yielding passive and lossless design [2]. These prerequisites can be formulated rigorously by extending the analytical model presented in [3] to RWGs, enabling semi-analytical resolution of the available degrees of freedom, i.e. the position of the loaded wire (x0, z0) and the load impedance density (the printed capacitor width). To demonstrate this design concept, we have used it to devise such a mode converter at 14 GHz; without any full-wave optimization, coupling efficiencies larger than 97% were achieved. These analytical results are verified via commercial solvers (CST), showing excellent agreement with theoretical predictions [Fig. 1(b), (c)]. The proposed scheme has immense potential in providing a way to develop efficient waveguide mode transducers without resorting to complex structures like fin-lines, and E-plane and H-Plane bends [1, 4, 5].
关键词： Floquet-Bloch modes,metagrating,TE10-to-TE20,rectangular waveguide,mode converter
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Robust Polarimetry with a Single Metagrating
摘要： One-shot optical polarimetry using ultra-thin nanostructured metagratings opens up new opportunities for diverse applications, facilitating the measurement of both classical and quantum polarization states. Despite the significant progress, there appeared fundamental limitations associated with a need to interleave multiple metagratings on a metasurface in order to split several distinct pairs of polarization components, which limited diffraction efficiency and negatively affected the beam quality. A recent study demonstrated polarimetry with a single metagrating, however it required an additional linear polarizer with the associated detrimental effects of attenuating the detected optical power, reducing the device compactness, and increasing the setup complexity. We formulate a new conceptual approach for polarization measurements with a single metagrating, which allows us to overcome the limitations that were inherent to the previous schemes. We find that those limitations occurred due to the attempts of replicating traditional polarimetry based on close-to-perfect polarizers, where each measurement characterizes a definite polarization component. Yet in general, metasurfaces can behave like sets of imperfect (partial) polarizers, and it is our key finding that full Stokes polarization reconstruction is possible in this regime. Specifically, we develop a rigorous polarimetry approach based on the positive operator-valued measure (POVM) formalism originating from quantum mechanics. This fundamentally lifts the restrictions on metasurface design and enables robust operation even under significant fabrication inaccuracies.
关键词： metagrating,polarization reconstruction,polarimetry,metasurface,POVM
更新于2025-09-11 14:15:04
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Ultranarrow-band metagrating absorbers for sensing and modulation
摘要： Nanostructured plasmonic metamaterials are an excellent platform for narrowband optical absorption, which has wide applications in sensing, filtering, modulation, and emission tailoring. However, achieving a subnanometer absorption bandwidth for optical sensing and dynamical control of light is still challenging. Here, we propose an asymmetric metagrating structure and make use of the propagating surface plasmonic mode that has a small dissipation rate, to achieve perfect optical absorption with a bandwidth of 0.28 nm near the wavelength of 1.55 μm. Our proposed structure can be used in solution environments as a chemical or biological sensor in the visible spectral range just by changing the structural parameters. The sensor possesses a sensitivity of 440 nm/RIU and figure of merit of 1333.33 RIU?1. In addition, by combining an organic electro-optic material with this metagrating, our device can be reconfigurable with a dynamic range of 15.52 dB. Therefore, our proposed metagrating platform not only works as an ultranarrow-band absorber, but also can be employed for optical sensing and dynamic control of light.
关键词： sensing,optical absorption,metagrating,plasmonic metamaterials,modulation
更新于2025-09-10 09:29:36