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Optical Nonlinearity of ZrS2 and Applications in Fiber Laser
摘要： Group VIB transition metal dichalcogenides (TMDs) have been successfully demonstrated as saturable absorbers (SAs) for pulsed fiber lasers. For the group comprising IVB TMDs, applications in this field remain unexplored. In this work, ZrS2-based SA is prepared by depositing a ZrS2 nanostructured film onto the side surface of a D-shaped fiber. The nonlinear optical properties of the prepared SA are investigated, which had a modulation depth of 3.3% and a saturable intensity of 13.26 MW/cm2. In a pump power range of 144–479 mW, the Er-doped fiber (EDF) laser with ZrS2 can operate in the dual-wavelength Q-switching state. The pulse duration declined from 10.0 μs down to 2.3 μs. The single pulse energy reached 53.0 nJ. The usage of ZrS2 as a SA for pulse generation in fiber lasers is presented for the first time. Compared to the experimental results of dual-wavelength Q-switched fiber lasers with two-dimensional (2D) materials, our laser performance was better. Our work indicates that the group comprising IVB TMD ZrS2 has bright prospects for nonlinear optical applications.
关键词： transition metal dichalcogenides,saturable absorbers,ZrS2
更新于2025-11-28 14:24:03
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A Facile Film-Nanoctahedron Assembly Route to Plasmonic Metamaterial Absorbers at Visible Frequencies
摘要： Plasmonic metamaterial absorbers (MAs) with broadband and near-perfect absorption properties in the visible region were successfully fabricated via a facile film-colloidal nanoparticle (NP) assembly method. In this approach, colloidal octahedral Au NPs were employed as the surface meta-atoms of MAs, while the nanoscale-thick SiO2 and Al films were used as the dielectric spacer and reflector respectively. It is worth noting that the Au nanoctahedron were randomly assembled onto the Al-SiO2 films, and no effort was made to precisely control their spatial arrangements. The optical characterization showed that the as-prepared MAs exhibited broadband high absorption (average absorptivity above 85%) within the whole visible spectrum for a broad range of incident angles (0°–60°). In particular, two polarization-independent near-perfect absorption peaks (absorptance above 99%) were recorded near 540 nm and 727 nm respectively. Moreover, the absorption properties of the MAs can be effectively controlled and tailored by varying the geometry (the thickness of the dielectric spacer and the surface coverages of the Au nanoctahedron). Electromagnetic simulations further demonstrated that enhanced Mie resonances and strong plasmonic coupling effects were critical for the designed MAs. This work here may provide an efficient and alternative route for the design of scalable visible light absorbers for applications such as solar cells, photothermalvoltaics, and biochemical sensors.
关键词： metamaterial absorbers,broadband and near-perfect absorption,aperiodic nanostructures,optical impedance matching,self-assembly
更新于2025-10-22 19:40:53
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Eumelanin for Nature‐Inspired UV‐Absorption Enhancement of Plastics
摘要： In the human body, the black-brown biopigment eumelanin blocks the harmful ultraviolet (UV) radiation. In the plastics industry, additives are often added to polymers to increase their UV-absorption properties. We herein report an assessment of the biopigment eumelanin as a nature-inspired additive for plastics to enhance their UV-absorption. Since eumelanin is produced by natural sources and is non-toxic, it is an interesting candidate in the field of sustainable plastic additives. In this work, eumelanin-including films of commercial ethylene-vinyl acetate copolymer (EVA), a plastic used for packaging applications, were obtained by melt-compounding and compression molding. The biopigment dispersion in the films was improved by means of the Melanin Free Acid treatment (MFA). It was observed that eumelanin amounts as low as 0.8% wt. cause an increase of the UV absorption, up to one order of magnitude in the UVA range. We also evaluated the effect of eumelanin on the thermal and photostability of the films: the biopigment proved to be double-edged, working both as UV-absorption enhancer and photo-prooxidant, as thermogravimetric analysis (TGA) and infrared (IR) spectroscopy revealed.
关键词： Eumelanin,Packaging,Melanin Free Acid,UV-absorbers,Ethylene-vinyl acetate copolymer,UV-aging
更新于2025-10-22 19:40:53
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On the Double Nano-Coned Graphite Metasurface-Based Multiband CIC Absorber
摘要： Spectral characteristics of nano-engineered absorber comprised of nano-cone-shaped multi-layered (or cascaded) graphene metasurface (that results in graphite medium) were investigated under different chemical potentials and incidence conditions. The configuration of the proposed absorber is of the conductor-insulator-conductor (CIC) kind, wherein the top and bottom metasurfaces are identical in a pattern having the array of graphite-cones. Such three-layer CIC absorber hosts relatively thick dielectric substrate sandwiched between graphite nano-cone-based metasurfaces, in order to trap incidence electromagnetic fields. The results in respect of absorbance revealed usefulness of the proposed structure in spectral filtering in the visible and far-infrared regimes. Also, the tuning feature of absorber through altering the chemical potential of metasurfaces was highlighted.
关键词： Nano-engineered mediums,Complex mediums,Metamaterial absorbers,Graphene structures
更新于2025-09-23 15:23:52
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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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Buchwald-Hartwig Coupling at the Naphthalenediimide Core: Access to Dendritic, Panchromatic NIR Absorbers with Exceptionally Low Band Gap
摘要： The ?rst successful Buchwald?Hartwig reaction at the naphthalenediimide core is reported, leading to the coupling of diverse secondary aromatic amines including dendritic donors. The G1-dendrimer-based donor exhibit blackish color, providing access to black absorbing systems. λ onset values up to 1070 nm was achieved, which is the maximum from a single NDI sca?old. These dyes also manifest multielectron reservoir properties. A total of eight-redox states with a band gap of ～0.95 eV was accomplished.
关键词： dendritic donors,low band gap,black absorbing systems,Buchwald?Hartwig reaction,naphthalenediimide,multielectron reservoir properties,NIR absorbers
更新于2025-09-23 15:21:21
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Experimental evaluation of volumetric solar absorbers – Ceramic foam vs. an innovative rotary disc absorber concept
摘要： This paper presents the experimental evaluation of two volumetric solar absorber concepts. It compares the thermal performance of conventional foam absorbers with that of an innovative rotary disc absorber design. The moving absorber showed advantages regarding air temperature stability at the outlet and better operability compared to the foam absorber. Unfortunately, it is shown that the innovative rotary disc design in its present form is not competitive, neither in terms of thermal performance, nor regarding mechanical reliability and robustness. The future task is therefore to optimize the mechanical design regarding thermal fatigue, in order to obtain a robust and durable rotary absorber that can be thoroughly evaluated experimentally.
关键词： volumetric solar absorbers,ceramic foam,thermal performance,rotary disc absorber,mechanical reliability
更新于2025-09-23 15:21:21
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Aperiodic order induced enhancement of weak nonlocality in multilayered dielectric metamaterials
摘要： Recent studies on fully dielectric multilayered metamaterials have shown that the negligibly small nonlocal effects (spatial dispersion) typically observed in the limit of deeply subwavelength layers may be significantly enhanced by peculiar boundary effects occurring in certain critical parameter regimes. These phenomena, observed so far in periodic and randomly disordered geometries, are manifested as strong differences between the exact optical response of finite-size metamaterial samples and the prediction from conventional effective-theory-medium models based on mixing formulas. Here, with specific focus on the Thue-Morse geometry, we make a first step toward extending the studies above to the middle ground of aperiodically ordered multilayers, lying in between perfect periodicity and disorder. We show that, also for these geometries, there exist critical parameter ranges that favor the buildup of boundary effects leading to strong enhancement of the (otherwise negligibly weak) nonlocality. However, the underlying mechanisms are fundamentally different from those observed in the periodic case and exhibit typical footprints (e.g., fractal gaps, quasilocalized states) that are distinctive of aperiodic order. The outcomes of our study indicate that aperiodic order plays a key role in the buildup of the aforementioned boundary effects and may also find potential applications to optical sensors, absorbers, and lasers.
关键词： absorbers,optical sensors,lasers,Thue-Morse geometry,aperiodic order,multilayered dielectric metamaterials,nonlocality
更新于2025-09-23 15:21:21
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Fabrication of ultra-thin, hydrophobic and flexible electromagnetic wave absorber sheets based on nano-carbon/carbonyl iron in a polypyrrole/silicone rubber matrix
摘要： In this work, electromagnetic (EM) wave absorbing properties of polypyrrole/silicone rubber (PP-SI) filled nano-carbon and carbonyl iron (CI) nanocomposites have been investigated in the X-band. The PP-SR matrix was provided by the incorporation of polypyrrole and liquid silicone rubber in the ratio of 10:90. The PP-SR serves not only as a matrix but also promotes the flexibility and EM wave absorption of the nanocomposite sheets. In the present research, the chemical, morphology, thermal, wetting, absorption, and mechanical properties of the EM wave absorber sheets are investigated. The EM wave absorber sheet with 3 wt% nano-carbon and 37 wt% CI and a thickness of 1 mm, exhibits a minimum reflection loss around ?13 dB at 10.27 GHz. The absorber sheet with an elongation of 520% could be qualified as a superior elastic sheet. The specimen represents higher thermal stability compared with pure SR, and the contact angle of the sheet proved that their surface should be hydrophobic.
关键词： Flexible wave absorbers,Silicone rubber,Polypyrrole,EM wave absorber sheets
更新于2025-09-23 15:21:21
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Saturable plasmonic metasurfaces for laser mode locking
摘要： Metamaterials are artificial materials made of subwavelength elementary cells that give rise to unexpected wave properties that do not exist naturally. However, these properties are generally achieved due to 3D patterning, which is hardly feasible at short wavelengths in the visible and near-infrared regions targeted by most photonic applications. To overcome this limitation, metasurfaces, which are the 2D counterparts of metamaterials, have emerged as promising platforms that are compatible with planar nanotechnologies and thus mass production, which platforms the properties of a metamaterial into a 2D sheet. In the linear regime, wavefront manipulation for lensing, holography, and polarization control has been achieved recently. Interest in metasurfaces operating in the nonlinear regime has also increased due to the ability of metasurfaces to efficiently convert incident light into harmonic frequencies with unusual polarization properties. However, to date, the nonlinear absorption of metasurfaces has been mostly ignored. Here, we demonstrate that plasmonic metasurfaces behave as saturable absorbers with modulation performances superior to the modulation performance of other 2D materials and exhibit unusual polarimetric nonlinear transfer functions. We quantify the link between saturable absorption, the plasmonic resonances of the unit cell and their distribution in a 2D metasurface, and finally provide a practical implementation by integrating the metasurfaces into a fiber laser cavity operating in pulsed regimes driven by the metasurface properties. As such, this work provides new perspectives on ultrathin nonlinear saturable absorbers for applications where tunable nonlinear transfer functions are needed, such as in ultrafast lasers or neuromorphic circuits.
关键词： fiber lasers,metamaterials,plasmonic,saturable absorbers,metasurfaces,nonlinear optics
更新于2025-09-23 15:21:01