In this paper, the properties of broadband absorbers for visible and near-infrared frequencies, based on multilayered metal-insulator (MI) structures have been analyzed. In our analysis, we have considered Titanium as metal and Silicon Nitride (Si3N4) as dielectric. In addition, the effect of the incident angle on the absorption properties of transverse magnetic and transverse electric polarized waves has been also investigated. Further, the influence of structural geometrical parameters has been studied in order to maximize the absorption and bandwidth. We believe that our results can be used as practical guidelines for realization of efficient broadband visible and infrared absorbers enabling applications as filters or absorbers for visible, infrared radiation and optical communications frequencies. The Finite Element Method has been used to carry the simulations.
In this paper the response of light propagation in hypercrystals (I.E, structures composed by metamaterial) have been numerically analyzed. The heterojunctions were considered to demonstrate that the optical properties change the behavior of the structure at visible and optical frequencies. The structure is composed by periodic layers to combine properties of photonic crystals and hyperbolic metamaterials that present different physical properties not found in nature. In most of cases have been composed by metal and semiconductor in alternate layers. To design a structure the Fibonacci's sequence was used to define the sequence order of layers. The materials used in simulations are Gold and Aluminum for as metals and Silicon for the as semiconductor. To compose a heterojunction photo detector part it was considered the low work-function metal Aluminum, for the intrinsic crystal Silicon, and high work-function metal Gold in this sequential layers.
In this paper the response of electromagnetic waves propagation in plasmonic structures composed by metals and dielectrics has been numerically analyzed. Thermal-optical coefficient was considered to demonstrate that the optical properties change the behavior of the structure at visible and infrared frequencies. The structure is composed by alternated thin layers of metal and semiconductor. The materials used in simulations are Silver for metal, Silica and Silicon for the semiconductors. Under temperature variations, these materials change their properties, like refractive index and can affect optical properties like absorbance, transmittance and reflectance. Besides, the incident angle was considerate as a variable. The Finite Element Method has been used to carry the simulations.
We proposed and analyzed the electromagnetic propagation response of multilayered metamaterial hypercrystals. The structure is composed by a periodic sequence of dielectric material and a metamaterial based on metal embedded in another dielectric. The final structure can exhibit asymmetrical optical properties and they can be used as mirrors, stop band filters and near unity absorbers for visible and infrared radiation. The propagation properties of the proposed hypercrystal can be tuned by adjusting their optical their geometrical and optical parameters.
In this article, we analyze the propagation response of Fibonacci based hypercrystals composed by metallic dielectric multilayered metamaterials. The estructure can be engineered to behave as mirrors or stop band filters and absorbers for visible and infrared radiation. The propagation properties of the proposed hypercrystal can be easily tunned and drastically changed by adjusting their geometrical and optical parameters.
The transmittance, reflectance and absorption of silver nanowires metamaterial embedded into a semiconductor matrix with optical gain are numerically investigated. Metamaterials may suffer from appreciable dissipative losses which are inherent for all plasmonic structures. The losses can significantly be reduced by introducing optical gain in the dielectric matrix by placing atomic or molecular impurities which are pumped by an external light source to create a population inversion. We numerically analyzed the optical properties when the semiconductor host material represents a gain medium. We calculate the transmittance, reflectance and absorption at normal incidence in the visible and near infrared ranges. We observed a peculiar behavior of their optical coefficients that can be explained by observing the field redistribution on the metamaterial.
We propose a strategy to design broadband absorbers. It is based on the apodization of a supercell composed of an array of subwavelength metallic-insulator gratings. The proposed absorber consists of grooves with variable depths in a metallic substrate filled with a dielectric material. It was demonstrated that the apodization procedure plays an important role in the required broadband operation of the proposed absorbers. The proposed absorber presented averaged values of absorption of the order of 94% for wavelengths from 700 to 2300 nm. The spectral response of the absorption coefficient, for a plane wave under normal incidence, has been calculated by using an efficient frequency-domain finite-element method.
The absorption and reflection characteristics of multilayered nanoplasmonic gratings with sub wavelength sizes are analyzed in details by using an efficient finite element method. The multilayered structures are composed by several layers of nanoparticles of metals such as Silver, Gold and Aluminum embedded in dielectric such as amorphous silicon over a metallic substrate. The propagations characteristics for several geometrical configurations are obtained and a broadband reflection or absorption covering the near infrared wavelengths has been observed. The proposed nanoplasmonic structures have a great potential for applications in photovoltaic cells or polarizers by improving their reflection or absorption efficiency. Peaks of reflection or absorption larger than 80% were obtained and their performance over the near infrared can be improved by adequately tuning their geometrical parameters, the refractive index and thickness of the layers as well as the nanoparticles shape and size.
Broadband nanostructured metallic-dielectric absorbers and reflectors are of great interest in integrated optics and they
have a great potential for applications like polarizers or reflectors for nanoantennas applications operating in optical
frequencies, covering the interval of the O-E-S-C-L-U bands. In this work, novel geometric and optical configurations
are numerically analyzed. The absorber or reflected central frequencies of the analyzed devices can be easily tuned over
the entire communications wavelength band by varying their geometrics and optical parameters Peaks of absorption
larger than 80% were obtained in optical wavelengths by using metals like silver and gold in combination with silica
substrates.
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