By using the rigid full-vectorial three-dimensional finite-difference time-domain method, we show that the enhanced transmission through a metallic film with a periodic array of subwavelength holes results from two different resonances: (i) localized waveguide resonances where each air hole can be considered as a section of metallic waveguide with both ends open to free space, forming a low-quality-factor resonator, and (ii) well-recognized surface plasmon resonances due to the periodicity. These two different resonances can be characterized from electromagnetic band structures in the structured metal film. In addition, we show that the shape effect in the enhanced transmission through the Au film with subwavelength holes is attributed to the localized waveguide resonance.
"The subwavelength rectangular slit arrays can enhance the transmission of linearly polarized light (perpendicular to the slit direction, i.e., angle α relative to x direction). Each unit can be considered as a localized linear polarizer and hence introduces a so-called Pancharatnam– Berry phase to the output beams   "
"The introduction of voids into a thin film significantly alters the characteristics of the medium, leading to exotic and interesting physical properties. In fact, such voids can lead to quantum effects in the conductivity  , enhanced optical transmission , artificial vortex pinning sites in superconductors  and magnonic crystals  , facilitating research and technological applications. Regarding magnetic materials, the inclusion of these artificial defects becomes an easy way to engineer their properties at micrometer and nanometer scales  . "
[Show abstract][Hide abstract] ABSTRACT: In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm. (Some figures may appear in colour only in the online journal)
"Very recently, an array of holes with very acute angles was found to exhibit a strong EOT effect caused by the LSP , an array of three-dimensional holes was also found that it has strong EOT effect induced by the LSP . The waveguide mode across each hole can also play an important role in the extraordinary transmission through Fabry–Perot resonance [14, 29]. Until now, there have been no reports about the extraordinary transmission in a non-planar asymmetric structure. "
[Show abstract][Hide abstract] ABSTRACT: We developed a method to fabricate a periodic array of three-dimensional crescent-like holes (3DCLH) via an inverted hemispherical colloidal lithography. It is found that there exists an extraordinary optical transmission in this non-planar perforated periodic array of 3DCLH when the electric field of the incident light is perpendicular to the cross-line of the crescent-like hole. This extraordinary optical peak is insensitive with the incident angles and sensitive with the angle between the electric field of the incident light to the cross-line of the 3DCLH. Numerical simulation based on finite-difference time-domain method reveals that this peak is caused by an asymmetric localized surface plasmon resonance. This structure might be useful for the optical sensing and optical-integrated circuits.
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