International Journal of

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We report an experimental study on optical and magneto-optical properties of Cesubstituted yttrium iron garnet thin films incorporating gold nanoparticles. Au nanoparticles were formed by heating Au thin film on cubic quartz and garnet substrate in vacuum chamber and a Ce:YIG layer was deposited on them by the aid of Pulsed laser deposition method. A large enhancement of the longitudinal Kerr effect was obtained in sample with Au nanoparticles on quartz substrate and the effect of substrate material on improving optical and magneto-optical response of samples were investigated.

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For a fiber optical surface plasmon resonance (SPR) sensor a short part of its cladding should be removed to coat a thin layer of a metal. Usually this is problematic when an optical fiber with small core diameter is used. In this paper, a new method using µliter droplet of the HF acid for short fiber optical taper fabrication is reported. Using this method in a multi-mode optical fiber with the core/cladding size of 50/125 µm a 2 mm long taper with 40 µm diameter is fabricated. Roughness of its surface is investigated using an atomic force microscopy. The measured mean value of the roughness is about 8 nm. A 60 nm thin layer of pure silver is coated on the taper surface in order to investigate its performance using a fiber optical SPR sensor.  Using this SPR fiber sensor measurement of the lead concentrations in water ranging from 0.1 to 10 part per million (ppm) is reported.

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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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Compared to the long history of plasmonic gratings, there are only a few studies regarding the bandgap in the propagation of plasmonic surface waves. Considering the previous studies on interpretation of plasmonic bandgap formation, we discuss this phenomenon using the effect of both surface plasmon polariton (SPP) and localized surface plasmon (LSP) for our fabricated one-dimensional metallic-polymeric grating. This structure is composed of metallic grating on the surface of PDMS with different concentration of embedded gold nanoparticles. By sweeping the incident angles, we have seen that the SPP, LSP and their coupling cause two gaps in reflection regime which are originated from SPP supported by thin film gold film and LSP supported by gold nanoparticles. The first gap is attributed to the patterned metallic film because it vanishes by increasing the nanoparticles which may destroy the pattern while the second gap can be formed by embedded nanoparticles because it becomes more considerable by raising the incubation time. Therefore, the drowning time of patterned samples (e.g. 24h, 48h, and 72h) in HAuCl4 plays the key role in adjustability of plasmonic bandgap. Notably, the interaction between SPP and LSP can be the origin of the shift in gap center from 300 to 550. To best of over knowledge, this study is the first study on the plasmonic band gap as a function of both SPP and LSP.

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In this paper, we study the entanglement of two-level atoms near a spherical silver nanoparticle. By employing the Von Neumann equation and utilizing of the electromagnetic Green’s tensor associated with a dispersive and dissipative dielectric sphere, the decay rates and the Lamb shift of the atomic system are obtained. Then, by using the concurrence measure, we calculate the degree of entanglement of the atomic system. We observe that the decay rates severely increase near the excitation frequency of the localized plasmon-polariton, while the concurrence value is nearly zero.
 
 

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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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In hollow nanostructures, the inner and outer surface plasmons couple together that provides interesting plasmonic properties resulting in the enhancement of the plasmonic field. In addition, triangular structures are interesting for plasmonic applications due to their sharp corners and low symmetry. In this work, gold triangular nanostructures with triangular (TTN) and circular (CTN) holes in their centers have been simulated using the FDTD method and their plasmonic properties have been compared. The extinction spectra of the structures display that CTN has only one plasmonic peak, whereas TTN has several plasmonic modes due to its lower symmetry. Each peak presents different interactions between the multipoles that understand from the charge density distribution. Also, the figure of merit (FOM) of the peaks has been calculated and a high value of 33 is obtained for one of the TTN modes, which is appropriate for sensing application.

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In this paper, an all optical graphene-based modulation approach is proposed induced by Modulation Instability (MI). The device structure is based on graphene sheets transferred on the both arms of a Mach-Zehnder interferometer to support amplified Surface Plasmon Polaritons (SPPs). Due to the nonlinear nature of MI to interfere in the modulation process, the proposed approach leads to an enhanced performance in comparison to the conventional Mach-Zehnder modulators; using a low power cw driving beam (~20 µW at λ=50 µm), a high speed modulation rate (~2 Tpps) and subsequently, a high depth (89%), wideband modulation (~81 GHz) can be resulted. Since the MI is a pre-state to the chaotic regime, the modulator can be also used for secure optical communication.

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In this paper, we propose a D-shaped plasmonic optical biosensor based on photonic crystal fiber (PCF) to detecting of the different materials such as water, blood plasma, Yd-10B and hemoglobin by using of the refractive index. The gold layer is coated on the polished surface of D-shaped fiber. To achieve the highest sensitivity of the proposed biosensor, we investigated the effects of variation of the gold layer thickness and the other structure parameters such as hole diameter (d) and the distance between two holes or Pitch (L). The results show that the most sensitivity of the proposed biosensor is 2506 nm per refractive index unit (nm/RIU) with the resolution of 1.25×10^-5 RIU, when d=1.4 µm and Λ=1.9 µm with the gold layer thickness of 45nm.

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Two-dimensional nanomaterials have attracted increasing attention for enhancing surface plasmon resonance (SPR) biosensors application. In this work, we use the graphene layer to improve the sensitivity of the SPR biosensors based on the conventional Kretschmann configuration. We employ Tungsten disulfide (WS₂) and Molybdenum disulfide (MoS₂) Two-dimensional materials as an interlayer to enhance the sensitivity of Au/Graphene biosensor in angle interrogation method. The transfer matrix method (TMM) is used to analyze the characteristics of the device. Results show that using WS₂ in Au/Graphene structure increases sensitivity by about 12.64%, which is higher than MoS₂. Combining graphene based SPR and ellipsometry as a highly sensitive, label-free, real-time, and versatile method can be used to measure a very small concentration of biomolecules, which leads to 170-fold enhancement compared to angle interrogation method and improves the detection accuracy and quality factor.

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Nobel metal nanoparticles (NPs) are widely used in various applications including optical and biological sensors, biomedicine, photocatalysts, electronics, and photovoltaic cells. The optical properties of gold NPs are surveyed in this paper under the Localized Surface Plasmon Resonance (LSPR) effect, which increases the light absorption and scattering at the LSPR wavelength. This LSPR frequency depends on various factors, including the shape and size of the particles as well as incident electromagnetic polarization. Here, the optical response of gold NPs with different shapes and sizes are investigated using the finite element method (FEM). The results show that the bandwidth, amplitude, and LSPR wavelength depend on the shape and dimensions of the NPs as well as the polarization of the incident light. The LSPR wavelength changes from 500 to 650 nm for different shapes of the gold NPs including sphere, octahedral, cube, ellipsoid, triangle, and with identical volume. To study the NP size effect on the optical properties, the absorption and scattering cross-sections (CSs) are also investigated for different sizes of NPs. The results show a redshift in the LSPR wavelength by increasing the NP size.

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In this work, a two-dimensional square periodic array was successfully transferred onto a rigid glass substrate during an innovative and simple-design two-step process of pattern transferring using Kapton tape and plasma technology. Flexible and stretchable, Kapton tape was selected for pattern transferring onto the glass for the first time herein; in parallel, the vacuum plasma treatment was utilized to improve surface adhesion properties and aid the pattern transferring process. The proposed 2D square plasmonic array supported the plasmon-induced transparency (PIT) phenomenon, which is caused by the excitation of surface plasmon resonances. The current study simulated the fabricated plasmonic structure using the finite-difference time-domain (FDTD) method and investigated the propagation of surface plasmon polariton (SPP) and cavity modes which enhanced transmission. This fabrication technique can offer new insights for micro/nanofabrication technology.

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Color vision deficiency (CVD), or color blindness, is a prevalent ocular disorder that hinders the recognition of different colors, affecting many people worldwide (8−10% of males and 0.4−0.5% of females). Recently, there has been a significant focus on plasmonic nanostructures as an alternative to chemical dyes for managing color blindness due to their remarkable characteristics and the tunability of plasmonic resonances. In this work, the plasmonic glasses based on silver nanoparticles with a TiO₂ thin layer coating were fabricated using the sputtering technique and proposed for blue-yellow (tritanopia) CVD management. The proposed plasmonic glasses based on silver nanoparticles are more selective than commercial Enchroma glasses because of the tunability of plasmonic properties of silver nanoparticles by controlling their morphology, which provides insights for applications of color vision deficiency improvement. Also, the antibacterial activity of the proposed plasmonic glasses based on silver nanoparticles was investigated against E. coli and S. aureus bacteria, which have exhibited effective antibacterial properties. The results indicate that the silver nanoparticle-based glasses not only aid in tritanopia management but also offer potential for antibacterial applications such as implant coatings.