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Although coupled plasmonic systems have been extensively studied in the past decades, their theoretical understanding is still far from satisfactory. Here, based on experimental and numerical studies on a series of symmetry-broken nano-patch plasmonic resonators, we found that Fano’s formula, widely used in modeling such systems previously, works well for one polarization but completely fails for another polarization. In contrast, a two-mode coupled-mode theory (CMT) can interpret all experimental results well. This motivated us to employ the CMT to establish a complete phase diagram for such coupled plasmonic systems, which not only revealed the diversified effects and their governing physics in different phase regions, but more importantly, also justifies the applicabilities of two simplified models (including Fano’s formula) derived previously. Our results present a unified picture for the distinct effects discovered in such systems, which can facilitate people’s understanding of the governing physics and can design functional devices facing requests for diversified applications.

Coupling is a ubiquitous phenomenon observed in various systems, which profoundly alters the original oscillation state of resonant systems and leads to the unique optical properties of metasurfaces. In this study, we introduce a terahertz (THz) tunable coupling metasurface characterized by a four-fold rotation (C4) symmetry-breaking structural array achieved through the incorporation of vanadium dioxide (VO2). This disruption of the C4 symmetry results in dynamically controlled electromagnetic interactions and couplings between excitation modes. The coupling between new resonant modes modifies the peak of electromagnetic-induced transparency (EIT) within the C4 symmetric metasurfaces, simulating the mutual interference process between modes. Additionally, breaking the C4 symmetry enhances the mirror asymmetry, and imparts distinct chiral properties in the far-field during the experimental process. This research demonstrates promising applications in diverse fields, including biological monitoring, light modulation, sensing, and nonlinear enhancement. [ABSTRACT FROM AUTHOR]

Dielectric nanostructures exhibit intriguing optical properties and outstanding advantages in designing optical nanoantennas and metasurfaces compared to plasmonic nanostructures. This study employs classical electrodynamic methods to comprehensively explore the scattering characteristics of silicon triangular nanoprisms in monomer and oligomer forms. For monomeric nanoprisms, the scattering spectra reveal two distinct and prominent resonance peaks attributed to magnetic dipole (MD) and electric dipole (ED) modes. Reducing interparticle gaps within dimeric structures leads to noticeable blueshifts in MD resonance peaks with stable intensities, in contrast to the nearly constant position and significantly reduced intensities of the ED resonance peaks. A pronounced Fano-like resonance was observed upon transitioning to tetrameric and hexameric configurations, resulting from the coupling between MD and ED modes. A broad resonance peak also emerges in the long-wavelength region due to MD-to-MD coupling. The simulations conducted herein hold significant theoretical implications, advancing our comprehension of the scattering properties of dielectric nanoparticles and contributing valuable insights into fundamental nanophotonics. [ABSTRACT FROM AUTHOR]

In order to improve the wear resistance of titanium alloy, a Ti5Si3/Ti3Al composite coating with improved wear resistance was successfully prepared by laser cladding TA2 titanium alloy using the double-layer presetting method of Ti-63 wt.% Al mixed powder layer/Si powder layer. The microstructure, phase composition and wear resistance of the coating were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and pin-disk friction and wear method. The results show that the coating is mainly composed of the Ti5Si3 primary phase and Ti5Si3/Ti3Al eutectic structure. The microhardness of the coating is higher than that of the matrix. The average microhardness of the coating is about 668 HV0.1, which is 3.34 times that of the matrix. The coating significantly improves the wear resistance of the TA2 matrix, and the mass wear rate is 1/5.79 of that of the TA2 matrix. The main wear mechanisms of the coating are abrasive wear, adhesive wear and oxidative wear, whereas the main wear mechanisms of the TA2 matrix are adhesive wear and oxidative wear. [ABSTRACT FROM AUTHOR]