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Directing energy into a sub-wavelength non-resonant metasurface across the visible spectrum.
摘要： Group 10 metals (i.e. Ni, Pd, Pt) catalyze a wide range of chemical transformations but the weak interaction of their nanoparticles with light hinders their development for photocatalytic applications. Conversely, coinage metals nanoparticles (particularly Ag and Au) exhibit intense localized surface plasmon resonances in the visible spectrum, but are relatively unreactive, limiting the scope and efficiency of their photochemical processes. Here we demonstrate the design, fabrication and characterization of a new structure containing a single layer of Pd nanoparticles that absorbs up to >98% of visible light. Furthermore, the wavelength of absorption is controlled throughout the visible range of the electromagnetic spectrum by modulating the thickness of a supporting metal oxide film. We show that the absorbed energy is concentrated in the nanoparticle layer, crucial for energy conversion applications including photocatalysis and photothermal processes.
关键词： photocatalysis,plasmonics,metasurfaces,palladium,Hot charge carriers,absorbers,critical coupling
更新于2025-09-23 15:23:52
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Weak Coupling, Strong Coupling, Critical Coupling and Fano Resonances: A Unifying Vision
摘要： The transversal concepts of weak, strong and critical coupling, and of Fano resonances, are analyzed within a unified framework which relies on a simple classical model of driven-dissipative coupled oscillators. A careful exploration of the system’s parameter space has led to the emergence of certain intriguing phenomena, which we named lineshape inheritance, universal absorption lineshape, and strong critical coupling. These concepts may be of relevance when attempting to understand the response of a diversity of systems, especially in the fields of (quantum) light-matter coupling, and of solid-state nanophysics, where the basic scheme of multi-oscillator dissipative resonances is often encountered.
关键词： strong coupling,Fano resonances,critical coupling,solid-state nanophysics,weak coupling,light-matter coupling
更新于2025-09-23 15:21:01
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Active control of narrowband total absorption based on terahertz hybrid Dirac semimetal-graphene metamaterials
摘要： A narrowband total absorber consists of a single layer of graphene, Photoactive Silicon and bulk Dirac semimetal (BDS) and has been studied in three different ways for light absorption control without changing the geometry of the structure. Numerical simulation results show that the total absorption is achieved in the narrow spectral range by the critical coupling achieved by the guided resonance, and the results are in good agreement with the coupled mode theory (CMT). Interestingly, this device exhibits exceptional polarization insensitivity and excellent absorption stability over a range of incident angles. In addition, the extremely remarkable sensing performance is more conducive to the application of bio-chemical sensors. In this article, we propose that this work achieves a significant enhancement of the interaction of light and matter in single-layer graphene without graphene plasmon response. This simple and easily fabricated narrowband total absorption structure has outstanding potential applications in the design of modulators, filters and photodetectors.
关键词： metamaterials,narrowband,absorption,critical coupling
更新于2025-09-23 15:19:57
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Double-mode absorption in double-defect photonic crystal with one graphene multilayer
摘要： In order to realize the double-mode absorption, double-defect photonic crystal is formed. For the upper defect, the graphene multilayer is placed on the top of photonic crystal acting as the surface defect, while for the one below, the pure dielectric destroying the periodicity of photonic crystal services as the internal defect. Depending on FP resonance, two modes achieve perfect absorption at critical coupling. Merely, the mode-dependences are different, so that these modes have different distinctly Q factors and can be tuned independently by changing the chemical potential of graphene and the size of defect. Combining the angle response, the independence-tuning of modes becomes more flexible. Besides, both of modes’ frequencies and amplitudes are enslaved to the layer number of graphene. And the period of photonic crystal affects directly the peak–peak distance and modes number.
关键词： Double-mode absorption,Double-defect photonic crystal,FP resonance,Critical coupling,Graphene multilayer
更新于2025-09-23 15:19:57
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Ultrabroadband plasmonic induced transparency in random metamaterial with nanocavity
摘要： A three-dimensional (3D) metamaterial is very easily assembled as a stacked structure with two physical vapor deposition layers, one metallic and one dielectric, and with a spray of gold nanospheres (GNS) on top. The first planar metasurface is a semicontinuous gold nanocomposite which is transformed into a “dark metasurface” when embedded in a dielectric nanocavity. The second metasurface is a radiative mirror composed of the self-arranged GNS at the nanocavity’s surface. The two random metasurfaces are strongly coupled through their near field inside the nanocavity. Plasmonic induced transparency is observed at normal incidence over a very wide spectral bandwidth of a few hundred terahertz from the visible to the NIR. The induced transmission maximum occurs in a spectral region where the scattering cross section from the GNS is maximum. Critical coupling between the two metasurfaces is achieved with multiple deposits of GNS and the transition from induced transparency to induced absorption is experimentally observed. Such a simple 3D metamaterial could be used to enhance non-linear optical effects, optical switching and slow light generation in the NIR.
关键词： Plasmonics,Nanocomposites,Nanospheres,Critical coupling,Metamaterials,Nano optics
更新于2025-09-19 17:13:59
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Tunable mid-infrared perfect absorber based on the critical coupling of graphene and black phosphorus nanoribbons
摘要： We demonstrate theoretically a wide-angle and tunable mid-infrared perfect absorber by coupling the graphene and black phosphorus plasmonics and utilizing the concept of critical coupling. With the black phosphorus nanoribbons alone, the localized surface plasmon resonances (LSPR) can be excited, while the absorption is small due to its single-layer thickness. A Fabry-Perot cavity is formed by adding an Au mirror as the substrate, which is separated from the black phosphorus by a dielectric spacer, hence the absorption is enhanced markedly due to critical coupling. In order to further enhance the absorption, a graphene grating is introduced on the top of black phosphorus and is separated by a dielectric slab. It is shown that the perfect absorption can be obtained due to the critical coupling of LSPR of black phosphorus and graphene. Based on these result, it is further demonstrated that the perfect absorption can work in large incident angle range, and the working wavelengths can be adjusted by the Fermi level of graphene. Our results provide a new avenue to achieve wide-angle and adjustable perfect absorption, and it may be beneficial for a variety of mid-infrared plasmonic applications.
关键词： plasmonics,mid-infrared,perfect absorber,graphene,black phosphorus,critical coupling
更新于2025-09-12 10:27:22
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Perfect near-infrared absorption of graphene with hybrid dielectric nanostructures
摘要： Near-infrared perfect wave harvesting of graphene is theoretically and numerically obtained in a hybrid dielectric configuration without assistance of a reflecting mirror. The absorption is increased 43-fold compared to a suspended graphene layer at normal incidence. The mechanism of perfect absorption is based on critical coupling with a guided resonance introduced by a silicon bar array and Fabry–Perot (FP) effect of a silicon oxide layer. This lossless design is expected to find applications to allow the active area with effective generation and fast transport of photocarriers, paving a new way for on-chip small-footprint ultrahigh responsivity and ultrahigh-speed photodetection in silicon photonics.
关键词： guided resonance,near-infrared absorption,hybrid dielectric nanostructures,graphene,Fabry–Perot effect,critical coupling
更新于2025-09-12 10:27:22
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[IEEE 2018 37th Chinese Control Conference (CCC) - Wuhan (2018.7.25-2018.7.27)] 2018 37th Chinese Control Conference (CCC) - Maximum Power Tracking of Wireless Power Transmission Systems Based on Critical Coupling Point Tracking
摘要： Power transmission is one of the key issues in wireless power transmission (WPT) systems and the maximum power transmission problem is considered in this paper. A load power model for the magnetic resonant coupling WPT system with string-to-string structure is carried out at first. And then, using the power normalization method, the theoretical performance is analyzed and a special working point called critical coupling point (CCP) is found. At this point, the system can transfer the possible maximum power. Thus, maximum power tracking (MPT) problem can be transformed into the critical coupling point tracking (CCPT) problem. Further, relationship between CCP and load resistance is analyzed. To achieve the maximum transmission power under any load, a DC-DC impedance conversion circuit is added at the receiving side so that the maximum power can be tracked by adjusting the equivalent load resistance dynamically. Simulation results show the effectiveness of the proposed method.
关键词： maximum power tracking,critical coupling point,wireless power transmission
更新于2025-09-04 15:30:14