Yuan-hao Chen

Robust multispectral transparency in continuous metal film structures via multiple near-field plasmon coupling by a finite-difference time-domain method

We propose a robust multispectral transparent plasmonic structure and calculate its transparency response by using the three-dimensional finite-difference time-domain (FDTD) method. The proposed structure is composed of a continuous ultrathin metal film sandwiched by double two-dimensional (2D) hexagonal non-close-packed metal-dielectric multilayer core-shell nanoparticle arrays. The top and bottom plasmonic arrays in such a structure, respectively, act as the light input and output couplers to carry out the efficient trapping and release of light. Near-perfect multispectral optical transparency in the visible and near-infrared regions is achieved theoretically. The calculated electric field distribution patterns show that the near-perfect multispectral optical transparency mainly originates from the excitation and hybridization of shell and core plasmon modes, strong near-field coupling of dipole plasmon modes between adjacent nanoparticles as well as the excitation of surface plasmon waves of the metal film. The robust transparency bands can be efficiently tuned in a large range by varying the structural parameters and the surrounding dielectric environment. The proposed structure also shows additional merits such as a deep sub-wavelength size and fully retained electrical and mechanical properties of the natural metal. These features might provide promising applications in highly integrated optoelectronic devices including plasmonic filters, nanoscale multiplexers, and non-linear optics.

Tunable Plasmon-Induced Transparency of Double Continuous Metal Films Sandwiched with a Plasmonic Array

Making a continuous metal film with near-unity transparency has received more and more attention in recent years because of its potential applications for various optoelectronic devices. Here, we theoretically show that a high tunable plasmon-induced transparency metal film structure can be performed by double continuous metal films inserted with a two-dimensional hexagonal lattice array of plasmonic nanopariticles. The proposed structure shows near-unity anti-reflection and intensively enhanced transmission via the cooperative effects of strong resonant near-field light input and output coupling by the plasmonic array and the excitation of surface electromagnetic waves of the metal films. The optical response can be efficiently mediated by varying the sizes of nanoparticles and the separated distance between the metal array and the metal films. With the merits of high transparency, sub-wavelength sizes and wholly retained metal characteristics including high conductivity via using the pure metallic materials, the structure proposed here suggests various potential applications in optoelectronic integrated circuits.

Narrowband Light Total Antireflection and Absorption in Metal Film–Array Structures by Plasmonic Near-Field Coupling

We study the cooperative effects between plasmon gap modes and optical cavity modes of a novel triple-layer structure consisting of double continuous gold films separated by a gold nanosphere array. Narrowband near-perfect antireflection of optical field is achieved for the first time due to the strong near-field light–matter interaction within the deep sub-wavelength gaps between adjacent nanospheres combined with the spatial field confinement effects of the optical cavity built by the double gold films. The coexistence cooperation of near-field dipole plasmon resonances and spatial optical field confinement presents more efficient light modification than that of the individual subsystem and may open a new approach to manage light flow. By varying the period of nanosphere array, the diameter of nanospheres, and the distance between the array and the film, optical behaviors of the proposed structure can be tuned in a wide range. High environmental sensitivity and large figure of merit factor are obtained using this structure as the detecting substrate. Furthermore, ultra-compact structure and high conduction suggest the proposed structure being a good candidate for potential applications in highly integrated optoelectronic devices, such as plasmonic filters and sensors.

Improved Broadband Near-Unity Light Transparency of a Metal Layer With Film-Coupled Dual Plasmonic Arrays

We report improved light transparency over a broad bandwidth in a metal-layered structure with two film-coupled subwavelength non-close-packed plasmonic arrays. Through the introduction of dual ultrathin dielectric spacing layers between the metal layer and the double plasmonic disk arrays, coupling of the input and output effects of light is efficiently enhanced through strong near-field localized plasmon resonances between adjacent plasmonic disks and the near-field plasmon cavity mode in the gap between the double plasmonic arrays and the metal layer. A broad bandwidth of 300 nm with near-unity light transmittance (above 90%) in the optical regime is achieved through the localized plasmon resonances and the symmetrical structure used here. The transparency of this structure is polarization independent and incident angle insensitive, and can be tuned by varying the structure parameters and the dielectric environment. In addition, the period of the plasmonic arrays and the thickness of the nanometer-separated plasmonic structure are less than λ /20 and λ/8, respectively. These values suggest that the proposed structure may have potential applications in deep subwavelength optoelectronic devices, including broadband optically transparent electrodes, highly integrated light input and output components, and plasmonic filters.

Tunable Extraordinary Optical Transmission in a Metal Film Perforated with Two-Level Subwavelength Cylindrical Holes

We propose a novel plasmonic metal structure composed of a silver film perforated with a two-dimensional square array of two-level cylindrical holes on a silica substrate. The transmission properties of this structure are theoretically calculated by the finite-difference time-domain (FDTD) method. Double-enhanced transmission peaks are achieved in the visible and infrared regions, which mainly originate from the excitation of localized surface plasmon resonances (LSPRs), the hybridization of plasmon modes, and the optical cavity mode formed in the holes. The enhanced transmission behaviors can be effectively tailored by changing the geometrical parameters and dielectric materials filled in the holes. These findings indicate that our proposed structure has potential applications in highly integrated optoelectronic devices.

Perfect superbroadband optical transparency from visible to near-infrared in a thin metallic film perforated with a cubic hole periodic array

Abstract. We propose a thin metallic film perforated with a hexagonal periodic array of cubic holes and calculate its optical properties through the three-dimensional finite-difference time-domain method. Perfect superbroadband optical transparency from visible to near-infrared is achieved with the transmittance up to 99% due to the excitation of surface plasmon polaritons on the nanopatterned metal surface, localized surface plasmons at the edges of the cubic holes, and their cooperative interaction. The perfect superbroadband optical transparency of the proposed structure mainly depends on the size of holes and the period of the cubic hole array, and the proposed structure with perfect superbroadband optical transparency can resist to the interference of surrounding dielectric environment, which would provide fascinating potential applications in absorbers, solar cells, and transparent electrodes.

Double-spectral enhanced optical transmission via the hybridization of plasmon modes in nanohole and nanocube arrays

We propose a novel plasmonic nanostructure composed of a silver (Ag) nanocube array coated on an Ag film perforated with a cubic nanohole array, and theoretically study its optical properties by the finite-difference time-domain method. Double greatly enhanced optical transmission bands in the visible and near-infrared regions are achieved via strong plasmon resonance coupling effects of the nanohole and nanocube arrays. The double-spectral enhanced optical transmission behaviors can be efficiently tailored by varying the widths, periods and heights of nanocubes and cubic nanoholes. The proposed structure may provide potential applications in deep subwavelength optoelectronic devices, including highly integrated light input and output components, sensors and plasmonic filters.