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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Dispersion Engineered Metasurfaces for Broadband Achromatic Optics
摘要： Chromatic aberrations in lenses are challenging to correct over large bandwidth. We show that dispersion-tailored and polarization-insensitive metasurfaces comprising counterintuitive anisotropic nanofins can correct the chromatic aberrations from simple singlet lenses to sophisticated microscope objectives with unprecedented compactness.
关键词： Nanophotonics,Dispersion engineering,Metasurfaces
更新于2025-09-11 14:15:04
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Broadband Linear-to-Circular Polarization Conversion Enabled by Birefringent Off-Resonance Reflective Metasurfaces
摘要： Due to the scarcity of circular polarization light sources, linear-to-circular polarization conversion is required to generate circularly polarized light for a variety of applications. Despite significant past efforts, broadband linear-to-circular polarization conversion remains elusive particularly in the terahertz and midinfrared frequency ranges. Here we propose a novel mechanism based on coupled mode theory, and experimentally demonstrate at terahertz frequencies that highly efficient (power conversion efficiency approaching unity) and ultrabroadband (fractional bandwidth up to 80%) linear-to-circular polarization conversion can be accomplished by the judicious design of birefringent metasurfaces. The underlying mechanism operates in the frequency range between well separated resonances, and relies upon the phase response of these resonances away from the resonant frequencies, as well as the balance of the resonant and nonresonant channels. This mechanism is applicable for any operating frequencies from microwave to visible. The present Letter potentially opens a wide range of opportunities in wireless communications, spectroscopy, and emergent quantum materials research where circularly polarized light is desired.
关键词： linear-to-circular polarization conversion,midinfrared,birefringent metasurfaces,terahertz,broadband
更新于2025-09-11 14:15:04
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Internal Structure Tailoring in 3D Nanoplasmonic Metasurface for Surface‐Enhanced Raman Spectroscopy
摘要： Tunable nanoplasmonic metasurfaces have resulted in many versatile platforms for sensing applications including surface-enhanced Raman scattering (SERS)-based detection. However, to date, their fabrication still faces challenges in uniformity, repeatability, and controllability. Here, a novel large-area and hierarchical nanoplasmonic array with controlled internal structure and tunable plasmonic properties is reported, relying on controllably tailoring the single nanosphere on a uniform double-layered array into a well-defined nanoflower structure. The fabrication involves colloidal self-assembly, lithography, and plasmonic metal coating. First, a uniformly distributed double-layered colloidal array is fabricated via an ethanol-assisted self-assembly technique. Next, with the help of inductively coupled plasma dry etching, the lower layer is transformed to the nanoflower array with well-defined petal shape. Subsequently, a gold film with controlled thickness is deposited onto the nanoflower structured array, resulting in a tunable optical and SERS-active enhancement effect. Furthermore, 3D finite-difference time-domain simulation shows multiple enhancement sites inside the nanoflower array. Such a brand-new 3D structured array has the potential for varied applications, ranging from SERS sensors to light regulation.
关键词： SERS,nanoplasmonic,metasurfaces,tunable optics,self-assembly
更新于2025-09-11 14:15:04
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New Class of RCS-Reduction Metasurfaces Based on Scattering Cancellation Using Array Theory
摘要： A technique to synthesize a new category of Radar Cross Section (RCS)-reduction metasurfaces is presented. The appealing feature of the proposed technique is that by representing the generalized Snell-Descartes’ law of reflection in the form of array factor, it unifies the two most widely studied and well established modern RCS-reduction methods: checkerboard metasurfaces (CMS) and gradient index metasurfaces (GIMS). More importantly, it refines the concepts of both of these metasurfaces and overcomes numerous limitations associated with them. It can synthesize the RCS-reduction metasurfaces which can be placed along with almost any existing metasurface, without replacing the original metasurface that may be designed to serve a specific purpose, to reduce its RCS. The proposed technique is fundamentally based on scattering cancellation, and it is validated using artificial magnetic conductor (AMC) technology for several configurations. Moreover, a phasor representation is developed and implemented for complex configurations to make the synthesis simpler and more insightful. Finally, to display the versatility of the proposed technique, an example of RCS-reduction metasurface has been synthesized and introduced to an existing high-gain metasurface ground plane available in the literature. This paper is confined to the conventional specular direction.
关键词： Scattering cancellation,Array Theory,metasurfaces,RCS reduction,Radar Cross Section,Bragg’s law,Generalized Snell-Descartes’ law,Schelkunoff Polynomial Method,Artificial Magnetic Conductor,Fermat’s principle,Huygens’ principle,Checkerboard
更新于2025-09-11 14:15:04
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Electrically programmable multi-purpose nonvolatile metasurface based on phase change materials
摘要： We propose an electrically programmable nonvolatile metasurface working at near-IR frequency (λ=1550 nm) based on ITO/Ge2Sb2Te5-ITO/Au crossbar structure. The proposed metasurface can dynamically change its optical function by modulating the crystallization level of Ge2Sb2Te5, which is a phase change material, at each pixel position individually by controlled electrical pulses. We design and optimize the metasurface by using finite-difference time-domain simulations and numerically demonstrate various optical functions including beam steering devices, flat lenses, optical vortex generators, and metasurface holograms with a single device geometry.
关键词： metasurfaces,phase change materials,spatial light modulators,reconfigurable metasurfaces,programmable metasurfaces
更新于2025-09-10 09:29:36
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Pancharatnam–Berry Optical Elements for Spin and Orbital Angular Momentum Division Demultiplexing
摘要： A Pancharatnam–Berry optical element is designed, fabricated, and optically characterized for the demultiplexing of beams with different polarization and orbital angular momentum states at the telecom wavelength of 1310 nm. The geometric phase control is achieved by fabricating properly-oriented subwavelength gratings on a silicon substrate, inducing a spatially-variant form birefringence. The digital grating pattern is transferred to the silicon substrate with a two-step nanofabrication protocol, using inductively coupled plasma reactive ion etching to transfer the resist pattern generated with high-resolution electron beam lithography. The optical characterization of the sample confirms the expected capability to sort circularly polarized optical beams with different handedness and orbital angular momentum. Encompassing optical element design and silicon photonics, the designed silicon metasurface paves the way to innovative devices for total angular momentum mode division multiplexing with unprecedented levels of integration.
关键词： subwavelength gratings,electron beam lithography,metasurfaces,silicon,orbital angular momentum,reactive ion etching,mode division multiplexing,polarization division multiplexing,Pancharatnam–Berry optical elements
更新于2025-09-10 09:29:36
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Subwavelength Artificial Structures: Opening a New Era for Engineering Optics
摘要： In the past centuries, the scale of engineering optics has evolved toward two opposite directions: one is represented by giant telescopes with apertures larger than tens of meters and the other is the rapidly developing micro/nano-optics and nanophotonics. At the nanoscale, subwavelength light–matter interaction is blended with classic and quantum effects in various functional materials such as noble metals, semiconductors, phase-change materials, and 2D materials, which provides unprecedented opportunities to upgrade the performance of classic optical devices and overcome the fundamental and engineering difficulties faced by traditional optical engineers. Here, the research motivations and recent advances in subwavelength artificial structures are summarized, with a particular emphasis on their practical applications in super-resolution and large-aperture imaging systems, as well as highly efficient and spectrally selective absorbers and emitters. The role of dispersion engineering and near-field coupling in the form of catenary optical fields is highlighted, which reveals a methodology to engineer the electromagnetic response of complex subwavelength structures. Challenges and tentative solutions are presented regarding multiscale design, optimization, fabrication, and system integration, with the hope of providing recipes to transform the theoretical and technological breakthroughs on subwavelength hierarchical structures to the next generation of engineering optics, namely Engineering Optics 2.0.
关键词： metasurfaces,plasmonics,flat optics,engineering optics,diffraction limit
更新于2025-09-10 09:29:36
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Mitigating Chromatic Dispersion with Hybrid Optical Metasurfaces
摘要： Metasurfaces control various properties of light via scattering across a large number of subwavelength-spaced nanostructures. Although metasurfaces appear to be ideal photonic platforms for realizing and designing miniaturized devices, their chromatic aberrations have hindered the large-scale deployment of this technology in numerous applications. Wavelength-dependent diffraction and resonant scattering effects usually limit their working operation wavelengths. In refractive optics, chromatic dispersion is a significant problem and is generally treated by cascading multiple lenses into achromatic doublets, triplets, and so on. Recently, broadband achromatic metalenses in the visible have been proposed to circumvent chromatic aberration but their throughput efficiency is still limited. Here, the dispersion of refractive components is corrected by leveraging the inherent dispersion of metasurfaces. Hybrid refractive-metasurface devices, with nondispersive refraction in the visible, are experimentally demonstrated. The dispersion of this hybrid component, characterized by using a Fourier plane imaging microscopy setup, is essentially achromatic over about 150 nm in the visible. Broadband focusing with composite plano-convex metasurface lenses is also proposed. These devices could find applications in numerous consumer optics, augmented reality components, and all applications including imaging for which monochromatic performance is not sufficient.
关键词： metasurfaces,nanophotonics,hybrid optics,dispersion
更新于2025-09-10 09:29:36
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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) - Vortex-sound diffusers using spiral metasurfaces
摘要： Metamaterials allow the accurate control of the acoustic scattering using subwavelength thickness panels. In this work, we report the scattering of spiral-shaped metasurfaces with practical application to sound diffusers. We analytically, numerically and experimentally show that bipolar spiral-shaped metasurfaces produce broadband non-specular reflection. We observe that the reflected energy can be scattered at higher diffraction orders and, due to the spiral geometry, the phase of the scattering field rotates producing a vortex in the near field. Thus, the specular component at normal incidence vanish. This produces a perfect correlation-scattering coefficient when comparing to a rigid flat reflector of same dimensions. In particular, the scattering of an Archimedes spiral metasurface is presented. We show that the scattering pattern corresponds to a high-order Bessel beam. The use of binary locally reacting surfaces with chiral geometry produce non-specular reflected patterns, allowing the use of these structures use as sound diffusers.
关键词： acoustic scattering,sound diffusers,metamaterials,Bessel beam,spiral-shaped metasurfaces
更新于2025-09-10 09:29:36
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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) - Decoupling of Two Closely Located Dipoles Using Metasurfaces of Resonant Dipoles and Split-Loop Resonators
摘要： We present numerical and experimental validations of decoupling between two very closely located dipole antennas using metasurfaces. Compared to decoupling by a single passive scatterer, decoupling by metasurfaces reduces negative effects over the radiated signal. Simulation and measurement results demonstrate the possibility of decoupling between two active dipoles using metasurfaces of passive dipoles and split-loop resonators (SLRs).
关键词： dipole antennas,MRI,split-loop resonators,decoupling,metasurfaces
更新于2025-09-10 09:29:36