Browsing by Subject "Electromagnetic wave polarization"
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Item Open Access An analysis for the broad-band absorption enhancement using plasmonic structures on uncooled infrared detector pixels(SPIE, 2012-05) Lüleç, S. Z.; Küçük, S. E.; Battal, Enes; Okyay, Ali Kemal; Tanrıkulu, M. Y.; Akın, T.This paper introduces an analysis on the absorption enhancement in uncooled infrared pixels using resonant plasmon modes in metal structures, and it reports, for the first time in literature, broad-band absorption enhancement using integrated plasmonic structures in microbolometers for unpolarized long-wave IR detection. Different plasmonic structures are designed and simulated on a stack of layers, namely gold, polyimide, and silicon nitride in order to enhance absorption at the long-wave infrared. The simulated structures are fabricated, and the reflectance measurements are conducted using an FTIR Ellipsometer in the 8-12 μm wavelength range. Finite difference time domain (FDTD) simulations are compared to experimental measurement results. Computational and experimental results show similar spectral reflection trends, verifying broad-band absorption enhancement in the spectral range of interest. Moreover, this paper computationally investigates pixel-wise absorption enhancement by plasmonic structures integrated with microbolometer pixels using the FDTD method. Special attention is given during the design to be able to implement the integrated plasmonic structures with the microbolometers without a need to modify the pre-determined microbolometer process flow. The optimized structure with plasmonic layer absorbs 84 % of the unpolarized radiation in the 8-12 μm spectral range on the average, which is a 22 % increase compared to a reference structure with no plasmonic design. Further improvement may be possible by designing multiply coupled resonant structures.Item Open Access Analysis of circular reflectors by complex source-dual series approach(IEEE, 1993-06-07) Oğuzer, Taner; Altıntaş, Ayhan; Nosich, A. L.In the present paper, two dimensional circular reflector antennas are analyzed by a rigorous analytical-numerical technique for both E and H polarization cases. The method is used in combination with the complex source approach. The convergence of the solution is guaranteed and any desired accuracy can be obtained. Some principal results of reflector antennas are examined by the exact circular reflector solution.Item Open Access Direct imaging of localized surface plasmon polaritons(Optical Society of America, 2011-08) Balcı, Sinan; Karademir, Ertuğrul; Kocabaş, Coşkun; Aydınlı, AtillaIn this Letter, we report on dark field imaging of localized surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by plasmonic coupled cavities. We image the light scattered from SPPs in the plasmonic cavities excited by a tunable light source. Tuning the excitation wavelength, we measure the localization and dispersion of the plasmonic cavity mode. Dark field imaging has been achieved in the Kretschmann configuration using a supercontinuum white-light laser equipped with an acoustooptic tunable filter. Polarization dependent spectroscopic reflection and dark field imaging measurements are correlated and found to be in agreement with finite-difference time-domain calculations.Item Open Access E-polarized beam scattering by an open cylindrical PEC strip having an arbitrary "conical-section" profile(John Wiley & Sons, Inc., 2001) Oğuzer, T.; Nosich, A. I.; Altintaş, A.Two-dimensional (2-D) scattering of waves by a conducting strip with a canonical profile is simulated in the E-polarization case. This analysis is performed by reducing a singular integral equation (IE) to the dual-series equations, and making their analytical regularization. Furthermore, the incident field is taken as a complex source point (CSP) beam. This is an extension of our previous studies about circular and parabolic reflector antennas. The algorithm features are demonstrated. Far-field characteristics are presented for quite large-size curves strips of elliptic, parabolic, and hyperbolic profiles.Item Open Access Hybrid plasmon-phonon polariton bands in graphene-hexagonal boron nitride metamaterials [Invited](Optical Society of America, 2017) Hajian, H.; Ghobadi, A.; Dereshgi, S. A.; Butun, B.; Özbay, EkmelWe theoretically investigate mid-infrared electromagnetic wave propagation in multilayered graphene-hexagonal boron nitride (hBN) metamaterials. Hexagonal boron nitride is a natural hyperbolic material that supports highly dispersive phonon polariton modes in two Reststrahlen bands with different types of hyperbolicity. Due to the hybridization of surface plasmon polaritons of graphene and hyperbolic phonon polaritons of hBN, each isolated unit cell of the graphene-hBN metamaterial supports hybrid plasmon-phonon polaritons (HPPs). Through the investigation of band structure of the metamaterial we find that, due to the coupling between the HPPs supported by each unit cell, the graphene-hBN metamaterial can support HPP bands. The dispersion of these bands can be noticeably modified for different thicknesses of hBN layers, leading to the appearance of bands with considerably flat dispersions. Moreover, analysis of light transmission through the metamaterial reveals that this system is capable of supporting high-k propagating HPPs. This characteristic makes graphene-hBN metamaterials very promising candidates for the modification of the spontaneous emission of a quantum emitter, hyperlensing, negative refraction, and waveguiding. © 2017 Optical Society of America.Item Open Access Lasing in a Slow Plasmon Moiré Cavity(American Chemical Society, 2015) Karademir, E.; Balci, S.; Kocabas, C.; Aydınlı, AtillaWe report on lasing from dye-based excitons coupled to slow plasmon states inside metallic Moiré cavities. Surface plasmon polaritons (SPPs) inside the cavity were slowed down to a maximum group velocity of 0.3c. Varying the modulation of the Moiré cavity, we tune the output wavelength of the plasmonic laser by varying the fast modulation period of the Moiré cavity. This work opens a new way to study SPP-matter interaction dynamics and plasmonic lasing with Bragg cavity confined slow plasmons.Item Open Access Modeling of ground-penetrating-radar antennas with shields and simulated absorbers(IEEE, 2001) Oğuz, U.; Gürel, LeventA three-dimensional (3-D) finite-difference time domain (FDTD) scheme is employed to simulate ground-penetrating radars. Conducting shield walls and absorbers are used to reduce the direct coupling to the receiver. Perfectly matched layer (PML) absorbing boundary conditions are used for matching the multi-layered media and simulating physical absorbers inside the FDTD computational domain. Targets are modeled by rectangular prisms of arbitrary permittivity and conductivity. The ground is modeled by homogeneous and lossless dielectric media.Item Open Access Radar cross-section study of cylindrical cavity-backed apertures with outer or inner material coating: the case of E-polarization(IEEE, 1993) Çolak, D.; Nosich, A. I.; Altintaş, A.A dual-series-based solution is obtained for the scattering of an E-polarized plane wave from a cavity-backed aperture which is formed by a slitted infinite circular cylinder coated with absorbing material. The material coating can be done on the inner or outer surface of the cylinder. For both cases, numerical results are presented for the radar cross section and comparisons are given for two different realistic absorbing materials. The radar cross-section results are also given for the aspect angle of the screen. Finally, the dependence of radar cross section on the thickness of the absorbing layer is presented. © 1993 IEEEItem Open Access RCS study of cylindrical cavity-backed apertures with outer or inner material coating: the case of e-polarization(IEEE, 1993) Çolak, Dilek; Altıntaş, Ayhan; Nosich, A. I.Cavity-backed apertures (CBA) are encountered as parts of any airborne or spaceborne radar targets. Most familiar of them are, probably, air inlets and engine tubes, known to contribute a great deal to radar cross section (RCS) of jet aircraft. In the present study, the dual-series-based solution is obtained for the scattering of an E-polarized plane wave from the cavity-backed aperture which is formed by a slitted infinite circular cylinder coated with absorptive material. The material coating can be done on the inner or outer surface of the cylinder. For both cases, numerical results are presented for the RCS and comparisons of the suppression of RCS are given for two different realistic absorptive materials.Item Open Access Simulation of TRT-configured ground-penetrating radars over heterogeneous grounds(IEEE, 2001) Oǧuz, Uğur; Gürel, LeventThe simulation of transmitter-reciever-transmitter (TRT) configured ground-penetrating radars over heterogeneous grounds was discussed. The finite-difference time-domain (FDTD) methods along with the perfectly-matched layer (PML) absorbing boundary conditions (ABC) were used for the simulations. Scattered-field image demonstrated that the buried target was easily detected when buried in a homogenous ground. Results show that the TRT-configured GPR is sensitive to surface roughness and the main source of noise is the detoriorations in the ground-air interface.Item Open Access Slow plasmons in grating cavities(SPIE, 2016) Aydınlı, Atilla; Karademir, E.; Balcı, S.; Kocabaş, CoşkunRecent research on surface plasmon polaritons and their applications have brought forward a wealth of information and continues to be of interest to many. In this report, we concentrate on propagating surface plasmon polaritons (SPPs) and their interaction with matter. Using grating based metallic structures, it is possible to control the electrodynamics of propagating SPPs. Biharmonic gratings loaded with periodic Si stripes allow excitation of SPPs that are localized inside the band gap with grating coupling, [1]. The cavity state is formed due to periodic effective index modulation obtained by one harmonic of the grating and loaded Si stripes. More complicated grating structures such as metallic Moiré surfaces have also been shown to form a localized state inside the band gap when excited with Kretschmann configuration, [1-6].Item Open Access Strong coupling between localized and propagating plasmon polaritons(OSA - The Optical Society, 2015) Balci, S.; Karademir, E.; Kocabas, C.We investigate plasmon-plasmon (PP) coupling in the strongly interacting regimes by using a tunable plasmonic platform consisting of triangular Ag nanoprisms placed nanometers away from Ag thin films. The nanoprisms are colloidally synthesized using a seed-mediated growth method and having size-tunable localized surface plasmon polariton (SPP) resonances immobilized on Si3N4 films. The PP coupling between the localized SPPs of metal nanoprisms and the propagating SPPs of the metal film is controlled by the nanoprism concentration and the plasmon damping in the metal film. Results reveal that Rabi splitting energy determining the strength of the coupling can reach up to several hundreds meV, thus demonstrating the ultrastrong coupling occurring between localized and propagating SPPs. The metal nanoparticle-metal thin film hybrid system over the square-centimeter areas presented here provides a unique configuration to study PP coupling all the way from the weak to ultrastrong coupling regimes in a broad range of wavelengths.Item Open Access Test of accuracy of the generalized boundary conditions in the scattering by thin dielectric strips(IEEE, 2014-05) Nosich, A. I.; Shapoval, O. V.; Sukharevsky, Ilya O.; Altıntaş, AyhanThe two-dimensional (2D) scattering of the E and H-polarized plane electromagnetic waves by a free-standing thinner than the wavelength dielectric strip is considered numerically. Two methods are compared: singular integral equations (SIE) on the strip median line obtained from the generalized boundary conditions for a thin dielectric layer and Muller boundary integral equations (BIE) for arbitrarily thick strip. The comparison shows the domain of acceptable accuracy of approximate model derived for thin dielectric strips. © 2014 IEEE.Item Open Access Three-dimensional FDTD modeling of a ground-penetrating radar(IEEE, 2000) Gürel, Levent; Oğuz, U.The finite-difference time-domain (FDTD) method is used to simulate three-dimensional (3-D) geometries of realistic ground-penetrating radar (GPR) scenarios. The radar unit is modeled with two transmitters and a receiver in order to cancel the direct signals emitted by the two transmitters at the receiver. The transmitting and receiving antennas are allowed to have arbitrary polarizations. Single or multiple dielectric and conducting buried targets are simulated. The buried objects are modeled as rectangular prisms and cylindrical disks. Perfectly-matched layer absorbing boundary conditions are adapted and used to terminate the FDTD computational domain, which contains a layered medium due to the ground-air interface.Item Open Access Transmitter-receiver-transmitter configurations of ground-penetrating radar(Wiley-Blackwell Publishing, Inc., 2002) Gürel, Levent; Oğuz, U.Three-dimensional ground-penetrating radar (GPR) geometries are simulated using the finite difference time domain (FDTD) method. The GPR is modeled with a receiver and two transmitters with arbitrary polarizations in order to cancel the direct signals emitted by the two transmitters at the receiver. This GPR configuration is used to simulate scenarios involving single or multiple targets with arbitrary sizes. The buried objects are modeled as cylindrical disks. Perfectly matched layer absorbing boundary conditions are used to terminate the layered FDTD computational domain.Item Open Access Transmitter-receiver-transmitter-configured ground-penetrating radars over randomly heterogeneous ground models(Wiley-Blackwell Publishing, Inc., 2002) Gürel, Levent; Oğuz, U.Ground-penetrating radar (GPR) problems are simulated using the finite-difference time-domain (FDTD) method. The GPR model is configured with arbitrarily polarized three antennas, two of which are transmitting antennas fed 180° out of phase. The receiver is placed in the middle of two transmitters, where it receives no direct coupling from the transmitting antennas. The ground is modeled as a dielectric, lossy, and heterogeneous medium. The performances of the transmitter-receiver-transmitter-configured GPRs above the heterogeneous ground models are investigated. The computational domain is terminated by perfectly matched layer (PML) absorbing boundaries. The PML is adapted to match both air and ground regions of the computation space.Item Open Access Ultra hybrid plasmonics: Strong coupling of plexcitons with plasmon polaritons(OSA - The Optical Society, 2015) Balci, S.; Kocabas, C.We report a ternary-coupled plasmonic system consisting of excitons of J-aggregated dye, localized surface plasmon polaritons of Ag nanoparticles, and propagating surface plasmon polaritons of continuous Ag film. J-aggregate dyes are uniformly self-assembled on colloidally synthesized Ag nanoprisms forming plexcitonic nanoparticles, which are placed at a distance nanometers away from the Ag thin film. The reflection measurements, corroborated by theoretical predictions, reveal that the strong coupling of plasmon polaritons and plexcitons results in a newly formed plasmon-exciton-plasmon hybridized state that we call here, reportedly for the first time, a plexcimon state. The hybrid plasmonic system shows dispersion characteristics similar to a coupled resonator optical waveguide. The group velocity of the plexcimon state approaches zero at the band edges. The ultrahybrid plasmonic system presented here is promising for a variety of light-matter interaction studies, including polariton lasers, plasmonic devices, plasmonic waveguiding, and spectroscopy.