Search for: plasmons
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    Coherent amplification and inversion less lasing of surface plasmon polaritons in a negative index metamaterial with a resonant atomic medium

    , Article Scientific Reports ; Volume 11, Issue 1 , 2021 ; 20452322 (ISSN) Asgarnezhad Zorgabad, S ; Sharif University of Technology
    Nature Research  2021
    Surface plasmon polaritons (SPPs) lasing requires population inversion, it is inefficient and possesses poor spectral properties. We develop an inversion-less concept for a quantum plasmonic waveguide that exploits unidirectional superradiant SPP (SSPP) emission of radiation to produce intense coherent surface plasmon beams. Our scheme includes a resonantly driven cold atomic medium in a lossless dielectric situated above an ultra-low loss negative index metamaterial (NIMM) layer. We propose generating unidirectional superradiant radiation of the plasmonic field within an atomic medium and a NIMM layer interface and achieve amplified SPPs by introducing phase-match between the superradiant... 

    An Efficient Circuit Model for the Analysis and Design of Rectangular Plasmonic Resonators

    , Article Plasmonics ; Volume 7, Issue 2 , June , 2012 , Pages 245-252 ; 15571955 (ISSN) Rezaei, M ; Miri, M ; Khavasi, A ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
    An efficient circuit model is proposed for studying the electromagnetic characteristics of rectangular plasmonic cavities. The proposed model comprised a finite size transmission line terminated by scalar load impedances at its both ends. It is capable of the fast extraction of resonance frequencies, quality factors, and mode profiles of plasmonic resonators made by carving rectangles in metallic medium. The accuracy of the proposed model is assessed using the fully numerical finite difference time domain technique. It is employed for analysis and design purposes  

    Ag Raman modes and ion-position dependence of the electronic structures of Y Ba2 Cu3 O7 and Y Ba2 Cu4 O8 from first principles

    , Article Physical Review B - Condensed Matter and Materials Physics ; Volume 76, Issue 5 , 2007 ; 10980121 (ISSN) Khosroabadi, H ; Mossalla, B ; Akhavan, M ; Sharif University of Technology
    Calculations of the frozen phonon for Ag Raman modes of the superconducting Y Ba2 Cu3 O7 and Y Ba2 Cu4 O8 systems have been carried out using the pseudopotential density functional theory in the local density approximation employing the VASP code. The eigenvalues and eigenvectors of the Ag Raman modes for the two systems have been calculated and compared with other experimental and computational studies. Electronic band structure and total density of states have been calculated for all the bare Ag modes for both systems. By calculating the changes in the bands intersecting the Fermi energy by ionic displacements, the ionic dependence of the electronic band structure in each of the Ag Raman... 

    Broadband, polarization-insensitive, and wide-angle optical absorber based on fractal plasmonics

    , Article IEEE Photonics Technology Letters ; Volume PP, Issue 99 , 2016 ; 10411135 (ISSN) Eshaghian Dorche, A ; Abdollahramezani, S ; Chizari, A ; Khavasi, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    In this paper, a plasmonic absorber consisting of a metal-dielectric-metal stack with a top layer of Sierpinski nanocarpet is theoretically investigated. Such a compact absorber depicts broadband angle-independent behavior over a wide optical wavelength range (400 700 nm) and a broad range of incidence angles (0 80). Including several feature sizes, such a fractal-like structure shows average simulated extinction response of 0:85 for either transverse electric or magnetic polarization states under normal incidence. Underlying mechanisms of absorbance due to excited surface plasmon modes as well as electric/magnetic dipole resonances are well revealed by investigating electric field, magnetic... 

    A graphene-based THz ring resonator for label-free sensing

    , Article IEEE Sensors Journal ; Volume 16, Issue 11 , 2016 , Pages 4338-4344 ; 1530437X (ISSN) Zangeneh Nejad, F ; Safian, R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    In this paper, we report on a novel resonant THz sensor for label-free analysis. The structure consists of a silicon nitride dielectric ring resonator vertically coupled to a thin layer of graphene strip ring resonator on top. The cladding is assumed to be porous alumina on the top of the graphene strip, which enhances the interaction of the surface plasmon wave and the target molecules. Finite difference time domain analysis is used to systematically design the structure and to investigate the performance of the sensor. Our simulations show that the proposed structure has larger refractive index sensitivity and lower intrinsic quality factor with respect to the similar optical structure. It... 

    A quantum description of linear, and non-linear optical interactions in arrays of plasmonic nanoparticles

    , Article Journal of Modern Optics ; Volume 65, Issue 10 , 2018 , Pages 1235-1244 ; 09500340 (ISSN) Arabahmadi, E ; Ahmadi, Z ; Rashidian, B ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    A quantum theory for describing the interaction of photons and plasmons, in one- and two-dimensional arrays is presented. Ohmic losses and inter-band transitions are not considered. We use macroscopic approach, and quantum field theory methods including S-matrix expansion, and Feynman diagrams for this purpose. Non-linear interactions are also studied, and increasing the probability of such interactions, and its application are also discussed. © 2018 Informa UK Limited, trading as Taylor & Francis Group  

    Design of a slit-groove coupler for unidirectional excitation of the guided surface plasmon polaritons through a plasmonic slot waveguide

    , Article Plasmonics ; Volume 12, Issue 1 , 2017 , Pages 131-138 ; 15571955 (ISSN) Eftekharinia, B ; Moshaii, A ; Dabirian, A ; Sharif University of Technology
    Springer New York LLC  2017
    In this paper, a plasmonic-photonic nanostructure has been introduced for efficient unidirectional coupling of free-space radiation to surface plasmon polariton (SPP) waves under normal illumination on a subwavelength slit. The structure consists of a conventional metallic slit-groove nanostructure integrated with a plasmonic waveguide to support SPP waves along the desired direction with a remarkable lateral confinement. The unidirectional coupling is achieved by using an integrated plasmonic distributed reflector designed under Bragg condition. This reflector basically distributes part of the light coupled through the slit into the SPP modes of the waveguide. Numerical simulations show... 

    Gold@Silver@Gold Core double-shell nanoparticles: synthesis and aggregation-enhanced two-photon photoluminescence evaluation

    , Article Plasmonics ; Volume 15, Issue 2 , 2020 , Pages 409-416 Daneshvar e Asl, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    Springer  2020
    A facile, straightforward, and low-cost method is proposed to synthesize gold@silver@gold core double-shell nanoparticles. The technique is a seed-mediated growth protocol that contains four steps of (1) gold seed synthesis, (2) gold seed growth, (3) silver layer coating through silver salt reduction, and (4) gold layer deposition via gold precursor reduction. The prepared nanoparticles had a narrow size distribution and the average particle size of 28 ± 1 nm. Cysteine was introduced to the nanoparticles solution as a coupling agent to assemble nanoparticles. Aggregation-induced two-photon photoluminescence enhancement of three types assembled nanoparticles, i.e., gold@silver@gold,... 

    Time dependence of the surface plasmon resonance of copper nanorods

    , Article Journal of Physics Condensed Matter ; Volume 19, Issue 44 , 2007 ; 09538984 (ISSN) Azarian, A ; Iraji zad, A ; Dolati, A ; Ghorbani, M ; Sharif University of Technology
    Copper nanorods have been synthesized by electrodeposition with different lengths in porous polycarbonate (PCT) membranes with a pore diameter of 50nm and a thickness of 4νm. The PCT membranes were dissolved in dichloromethane (CH2Cl2) and the solvent was replaced by methanol solutions. Extinction peaks at 587, 581 and 574nm were observed for the Cu nanorods with aspect ratio R = 6,8 and 10 in methanol, respectively. Polarization of the molecules of the medium around the wires changes the dielectric constant of the medium. Hence, the wavelength of the extinction peaks does not shows good agreement with calculations that were done on basis of Gans' theory with nominal dielectric constant of... 

    High-performance UV‐Vis-NIR photodetectors based on plasmonic effect in Au nanoparticles/ZnO nanofibers

    , Article Applied Surface Science ; Volume 483 , 2019 , Pages 1110-1117 ; 01694332 (ISSN) Hosseini, Z. S ; Arab Bafrani, H ; Naseri, A ; Moshfegh, A. Z ; Sharif University of Technology
    Elsevier B.V  2019
    In this study, UV‐Vis-NIR photodetectors based on decorated ZnO nanofibers (NFs) with optimized coverage of Au nanoparticles (NPs) fabricated via combined simple electrospinning and sputtering techniques are introduced. The effect of different coverages of Au NPs resulted from different Au nominal layer thicknesses on the morphology and optical properties of the ZnO fibers are investigated through various characterization methods. It is discovered that 4 nm Au nominal thickness provides the highest UV on/off ratio (~460), responsivity (~332 A/W), detectivity (~2.93×10 11 Jones) as well as faster rise and decay times as compared to pure ZnO nanofibers. A broad spectral response from UV to NIR... 

    Investigating Frequency, Phase, and Amplitude Singularities in a Hybrid Plasmonic System

    , M.Sc. Thesis Sharif University of Technology Dastangoo, Fatemeh (Author) ; Sadighi Bonabi, Rasoul (Supervisor)
    In recent years, nanoplasmonic quantum has been an active and developing field, resulting in several quanta and nonlinear qualities in the time-frequency interval, such as the creation of coherent single photons, nonlinear observation in nanometer dimensions, high-speed optical switch, etc. In the meantime, the controlled emission of surface polaritons resulted in the development of new devices such as nanolasers , subwavelength diodes, and high-speed phase and amplitude modulators , all of which have had a significant impact on the development of technology in very miniature dimensions. Numerous approaches have been proposed for the manufacturing of nanolasers, or reinforced plasmon... 

    THz plasmonic devices based on an array of metallic posts in a parallel-plate waveguide

    , Article International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, Mainz ; 2013 ; 21622027 (ISSN) ; 9781467347174 (ISBN) Ahmadi Boroujeni, M ; Shahabadi, M ; Altmann, K ; Sharif University of Technology
    An array of metallic posts sandwiched between two parallel metal plates supports highly-confined surface waves that can be regarded as spoof surface plasmons. This structure which is called the parallel-plate ladder waveguide (PPLWG) can be used for implementing THz guided-wave devices. In this paper, the effect of post shapes on waveguiding characteristics of PPLWG is analyzed and realization of certain devices such as couplers using the proposed structure is investigated  

    Wannier functions for surface plasmon polaritons

    , Article Proceedings of SPIE - The International Society for Optical Engineering ; Volume 7946 , 2011 ; 0277786X (ISSN) ; 9780819484833 (ISBN) Hazeghi, A ; Khorasani, S ; The Society of Photo-Optical Instrumentation Engineers (SPIE) ; Sharif University of Technology
    Wannier functions are real space basis functions which are not unique due to an arbitrary phase factor in the Bloch envelope function. We exploit this property to optimize a spread functional numerically using an accelerated steepest descent, and obtain the maximally confined set of Wannier functions, which are obtained for the first time in the area of planar plasmonics and conducting interfaces  

    An analytical formulation enabling analysis of resonance eigenmodes and their interferences in scattering from plasmonic nanostructures, applications in engineering the radiation loss

    , Article IEEE Journal of Quantum Electronics ; Volume PP, Issue 99 , 2016 ; 00189197 (ISSN) Khajeahsani, M. S ; Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    An analytic formulation revealing exact contribution of different factors affecting the interference interaction between eigenmodes of a scatterer is presented by utilizing our previously reported modal scattering power formula. For special case of arbitrary multilayer concentric and nonconcentric nanoshells, a recursive method for analytically calculating the T-matrix, and each of these factors is derived. Results for a three layer structure showing the conditions for constructive and destructive interference interactions are discussed in details. It is shown that the interference interaction can occur in the vicinity of the overlapping resonance frequencies of the two spatially overlapping... 

    Tunable spherical graphene surface plasmon amplification by stimulated emission of radiation

    , Article Journal of Nanophotonics ; Volume 13, Issue 2 , 2019 ; 19342608 (ISSN) Ardakani, S. B ; Faez, R ; Sharif University of Technology
    SPIE  2019
    A structure is suggested for spasing. The presented surface plasmon amplification by stimulated emission of Radiation (SPASER) is made up of a graphene nanosphere, which supports localized surface plasmon modes, and a quantum dot array, acting as a gain medium. The gain medium is pumped by an external light source. Since all the plasmons are carried on a graphene platform, the structure features coherent surface plasmons with high confinement and large life time. All the structures are analyzed theoretically using full quantum mechanical description. The main advantage of the proposed SPASER is its simple tuning capability of changing graphene's Fermi level, which is performed by either... 

    Plasmonic fractals: Ultrabroadband light trapping in thin film solar cells by a Sierpinski nanocarpet

    , Article Optical and Quantum Electronics ; Vol. 46, issue. 6 , 2014 , pp. 751-757 ; ISSN: 03068919 Kazerooni, H ; Khavasi, A ; Sharif University of Technology
    Plasmonic Sierpinski nanocarpet as back structure for a thin film Si solar cell is investigated. We demonstrate that ultra-broadband light trapping can be obtained by placing square metallic nanoridges with Sierpinski pattern on the back contact of the thin film solar cell. The multiple-scale plasmonic fractal structure allows excitation of localized surface plasmons and surface plasmon polaritons in multiple wavelengths leading to obvious absorption enhancements in a wide frequency range. Full wave simulations show that 109 % increase of the short-circuit current density for a 200 nm thick solar cell, is achievable by the proposed fractal back structure. The amount of light absorbed in the... 

    Investigation of a quasi-3D plasmonic nanostructure for TE and TM polarizations

    , Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 11 , 2014 , p. 2838-2844 Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
    Quasi-3D plasmonic nanostructures consisting of a metallic film perforated as an array of nanoholes, separated by a gap from a nanodisk array, are theoretically investigated under plane wave illumination with transverse electric and transverse magnetic polarizations. The results are compared with the results of a simple nanodisk array. A full discussion involving the couplings between plasmon resonance in nanodisks, surface plasmon polaritons on the interfaces of metallic film, and different diffractive grating orders that contribute in the couplings will be presented. The large difference between the plasmon behavior of the nanodisk array alone and nanodisk array in the presence of nanohole... 

    Enhanced optical transmission through metallic holes array: role of te polarization in spp excitation

    , Article Plasmonics ; Volume 8, Issue 2 , June , 2013 , Pages 403-409 ; 15571955 (ISSN) Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
    Optical transmission through double-layer metallic subwavelength holes array is studied under oblique incidence by split-field finite-difference time-domain method. Both TM and TE polarizations are investigated. It is proved that the transmission peaks can also be observed for TE polarization due to the excitation of surface plasmon polaritons (SPP) through diffraction orders. By changing the incident angle, these transmission peaks follow the SPP wavelength shift. The field profiles, even for the field components not present in the incident field, clearly show the SPP excitation. The mechanism of enhanced transmission will be fully discussed  

    Optical detection of some hydrazine compounds based on the surface plasmon resonance band of silver nanoparticles

    , Article Spectroscopy Letters ; Volume 46, Issue 1 , 2013 , Pages 73-80 ; 00387010 (ISSN) Tashkhourian, J ; Hormozi Nezhad, M. R ; Fotovat, M ; Sharif University of Technology
    An indirect colorimetric method is presented for spectrophotometric determination of hydrazine, phenylhydrazine, and isoniazid. Reduction of silver ions to silver nanoparticles (AgNPs) by these analytes as active reducing agents in the presence of polyvinylpyrrolidone (PVP) and also cetyltrimethylammonium chloride (CTAC) as a stabilizer is the basis of the proposed method. The changes in plasmon absorbance of the AgNPs at λ = 415 nm in the presence of PVP were proportional to concentration of hydrazine, phenylhydrazine, and isoniazid in the ranges of 4.0-150.0 μM, 1.0-55.0 μM, and 2.0-30.0 μM, respectively, and the detection limit obtained was 0.79 μM. In the presence of CTAC, the linear... 

    Sensitive spectrophotometric detection of dopamine, levodopa and adrenaline using surface plasmon resonance band of silver nanoparticles

    , Article Journal of the Iranian Chemical Society ; Volume 7, Issue SUPPL. 1 , 2010 , Pages S83-S91 ; 1735207X (ISSN) Hormozi Nezhad, M. R ; Tashkhourian, J ; Khodaveisi, J ; Sharif University of Technology
    A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag+ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10-6- 2.0x10-5 M, 1.6x10-7 - 1.0×10-5 M,...