International Journal of

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We have proposed a new ultra-compact optical demultiplexer based on metal-insulator-metal plasmonic waveguides aperture-coupled to the ring resonators. Our proposed device has high performance, small footprint, and high potential for integration and development to more channels.

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In this paper, the scattering of a plane monochromatic electromagnetic wave from a nanowire with circular cross-section in the transverse electric (TE) mode is simulated using the well-known Stratton-Chu surface integral equations. For an ordinary dielectric nanowire the refraction phenomenon is nicely simulated. In the case of a plasmonic nanowire no sign of surface plasmon excitation and propagation is seen. Transition from electrostatic regime to the geometrical shadow through diffraction regime by decreasing the light wavelength is also observable.

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Nanostructures of noble metal materials have been used in organic solar cells for enhancement of performance and light trapping. In this study, we have introduced branched silver cauliflower-like nanopatterns as sub-wavelength structured metal grating in organic solar cells. Self-assembled fabrication process of branched nanopatterns was carried out on a bio-template of cicada wing nanonipple arrays using a gas aggregation dc magnetron sputtering nanocluster source without size filtration. The branched nanostructures provide surface gaps with dimensions near the organic exciton diffusion length, which prevents recombination of charge carriers. An increased power conversion efficiency of 14.8% compared to that of the planar device was achieved mainly due to the enhancement in the short-circuit current density. Besides, these branched cauliflower-like nanopatterns had enhanced optical light absorption in the solar cell as a result of enhancing the optical path length of the reflected light in the active layer and plasmonic effects of the noble metal material.

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In this article, the effect of plasmonics properties of metal nanorods and nanoparticles on solar cell performance were investigated and simulated. Due to the classic solar cell disadvantages, it seems that a plasmonic solar cell is one of these methods. In plasmonic solar cells, because of plasmonic effect, a high electric field builds around metal nanoparticles so that high conversion efficiency is available. In this study, it is shown that the near-field electromagnetic wave severely affects the generation rate, which handles the carrier’s generation in the solar cell equations. By manipulating the plasmonic properties of nanoparticles or nanorods in solar cells structure, distribution of the electromagnetic fields are altered. In this work, optical power and generation rate related to the poynting vector is calculated. So, for improving the generation rate as an important parameter in solar cells, the alteration of nanoparticles or nanorods material, shape, inter-distance between them and medium material, are done. Finally, the comparison between classical solar cell and our improved structure is performed.

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In this paper the transmittance of metal-insulator-metal (MIM) waveguides containing semi-circular ring shaped and rectangular ring shaped grooves are investigated. By varying groove parameters their effects on the transmittance of the MIM waveguides are investigated. The results show that the transmittance spectra of the waveguides have maximum and minimum points, and by using appropriate parameters for the grooves it is possible to make the transmittance maximum or minimum at a required frequency. Therefore by using the ring shaped grooves in the MIM waveguides a frequency splitter is designed. In comparison the efficiency of a MIM waveguide containing the ring shaped groove, on blocking the transmission of a required frequency, is higher than the efficiency of a MIM waveguide containing tooth shaped groove.

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To investigate the plasmonic effect in perovskite solar cells, the effect of depositing Au@SiO₂ nanoparticles on the top and the bottom of mesoporous TiO₂ layers was studied. First, Au@SiO₂ nanoparticles were synthesized. The particles were then deposited at the different interfaces of mesoporous TiO₂ layers. Although the two structures show approximately similar optical absorption, only cells with Au@SiO₂ nanoparticles deposited at the bottom of the mesoporous TiO₂ layers demonstrated an improved photocurrent performance compared to the reference cells. This structure shows a short-circuit current density (JSC) of 20.7 mA/cm² and open circuit voltage of 1081 mV. This enhancement may be attributed either to the interface surface engineering or plasmonic resonance of Au@SiO₂ nanoparticles depends to the NPs size and position.  

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In this article, the effect of plasmonic properties of metal nanoparticles with different shapes, and moreover, their plasmonic-photonic interaction, on solar cell performance were investigated and simulated. Because of low conversion efficiency and then high cost of solar cells, it is difficult to commercialize and replace them with conventional energy resources. But in recent years, the plasmonic solar cell has been very popular. In this study, it is shown that the enhancement of near-field electromagnetic waves severely affects the generation rate, which handles the carrier’s generation in the solar cell equations and causes alteration of the photocurrent. This means that by manipulating the plasmonic properties of nanoparticles (shape and density) and their interaction with photons in solar cell structure, distribution of electromagnetic fields will be altered. Hence, the optical power related to the poynting vector is changed. So, with the aim of improving the solar cell some important parameters such as alteration of nanoparticle shape and their inter-distance were investigated. Finally, a comparison between traditional solar cells and our improved structure was undertaken.

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In this paper, we perform a detailed study of the spectral response of the gold U-shaped nano-structures for different geometrical parameters and polarizations in order to obtain significant localization factor in the wavelength 1.55 μm. The obtained near-field distribution of electric fields reveals that resonances in these nano-structures correspond to the even and odd plasmonic modes depending on the geometrical parameters and polarization directions. Considerably large localization factor is obtained for the first odd mode in specific geometrical parameters. Then, this structure is considered to be surrounded by a typical second-order nonlinear dielectric. The effective susceptibility is calculated for the considered structure, using the nonlinear retrieval method, to demonstrate the enhanced second-harmonic generation quantitatively.   In order to represent the applicability of the investigated structure in nano-scale light sources and frequency doublers, its second harmonic generation efficiency is compared with the efficiency of the nonlinear dielectric alone with the same dimensions.

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Silver nanowires are the favorable material in many applications based on their plasmonic double resonance in the visible region. In this paper, thin films of Poly-vinyl-pyrrolidone (PVP) doped with Silver nanowires (Ag NWs) in different concentrations have been prepared. The plasmonic imaging system using a high numerical aperture objective lens excite the Surface Plasmon in these structures. The hot spot results from reflected light intensity of surface plasmon resonance (SPR) proved that increasing of concentration of Silver nanowires yields to get better hot spot in plasmonic imaging systems by choosing the appropriate wavelength. These obtained results accompanying with third order nonlinear investigations show the ability of samples usage in thermoplasmonic applications.

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The absorption cross-section of gold and silver nanoparticles has been demonstrated in confined wavelength spectra based on Mie's theory. For this purpose, the numerical study performed with COMSOL for defined particle size to clarify absorption spectra and final results have been compared with experimental data to express the absorption peak occurs in higher wavelength for large particle size which is in around 530 nanometers for gold and 400 nanometer for silver particles.  These results show that particle size affects directly on absorption spectra of metallic nanoparticles.

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Recently, color production by using plasmonic structures has widely been studied. In this research, a flat and flexible two-dimensional Kapton-copper plasmonic crystal with very low thickness has been fabricated in a new and optimal way. Color production is performed using our proposed plasmonic structure and different colors are achieved by changing the incidence angle of light. Also, the plasmonic resonance response of the fabricated structure has been recorded at the incidence angle of 58 degrees. Advantages of our proposed structure are low cost, easy fabrication, and very small dimensions, and thus this research can be useful due to the increasing needs for the integration and miniaturizing of optical devices in modern nanophotonic systems.

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Plasmonic nanosensors have emerged as a powerful tool for biosensing and other applications. Therefore, efforts are underway to achieve higher sensitivity for these nanosensors. In line with this goal, we have investigated the sensitivity of silver square and triangular chiral nanosensors based on two strategies, Localized Surface Plasmon Resonance (LSPR)-based and Circular Dichroism (CD)-based sensing. Chiral nanostructure parameters (height, diameter) and the angle of incidence light have been optimized with calculation method (3-D finite-difference time-domain (3-D- FDTD)) in order to obtain best localized surface plasmon resonance and consequently the highest sensitivity. The calculation results show that sensitivitys~1727 and 1658nmRIU^-1 can be achieved in LSPR- and CD-based sensing method respectively for square chiral nanostructure, which are significantly more than previous works.

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In this paper, the frequency response of a detector antenna is investigated when a layer of dielectric is placed on it. For this purpose, the surface wave theory has been used to explain the propagation of the current pulses in the antenna electrodes. Examinations are also performed of the propagation spectra of two types of terahertz antennas, bow-tie and dipole (with LT-GaAs substrates), on which the dielectrics of gallium arsenide and silica are located. These antennas are simulated through the CST software (FDTD method). The simulations show that the presence of a surrounding dielectric on the surface of an antenna affects the velocity of the current pulse propagation on the electrodes. It is also shown that the change in the thickness and position of the surrounding dielectric have a negative effect on quality of detector antenna by shift its spectral response to lower frequencies.

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ta charset="UTF-8" >Color vision deficiency (CVD) is a disorder in which patients cannot distinguish specific colors. In the last few decades, the researchers have attempted to find a solution to cure this deficiency, despite valuable attempts by scientists, a promising and effective remedy has not been attained yet. As curing of CVD with the tinted or dyed glasses and lenses in colorblind patients is not satisfying, in this work, we have studied a novel and simple method using plasmonic gold nanoparticles in the contact lenses to improve CVD based on surface plasmon resonance of gold nanoparticles in the visible spectral range. In this technique, the dispersion of gold particles into the contact lens and transforming them to plasmonic gold nanoparticles provides a color filter that can be applied in the correction of the red-green type of colorblindness.The modified lens blocks a narrow band centered at 560nm, the wavelength that vision spectra of CVD patients overlap at those ones.