Browsing by Subject "Sub-wavelength"

Now showing 1 - 8 of 8

Open Access
Diodelike asymmetric transmission of linearly polarized waves using magnetoelectric coupling and electromagnetic wave tunneling
(American Physical Society, 2012-05-24) Mutlu, M.; Akosman, A. E.; Serebryannikov, A. E.; Özbay, Ekmel
An asymmetric, reciprocal, diffraction-free transmission of linearly polarized waves in a new diodelike, three-layer, ultrathin, chiral structure is studied theoretically and experimentally. The exploited physical mechanism is based on the maximization of the cross-polarized transmission in one direction due to the polarization selectivity dictated by the peculiar eigenstate combination, which is efficiently controlled by the electromagnetic tunneling through the metallic subwavelength mesh sandwiched between these layers. Simulation and microwave experiment results demonstrate a nearly total intensity transmission at normal incidence in one direction and a small intensity transmission in the opposite direction.
Unknown
Dipole antenna couplers for subwavelength metal-insulator-metal waveguides
(Optical Society of America, 2010) Onbasli, M.C.; Okyay, Ali Kemal
Near-infrared light (λ=1550 nm) was coupled into a 100-nm-core Ag/SiO2/Ag waveguide using dipole antennas. We demonstrate that using antennas, the field intensity inside the waveguide can be enhanced by changing the antenna size and location. © 2010 OSA /FiO/LS 2010.
Open Access
Experimental verification of metamaterial based subwavelength microwave absorbers
(American Institute of Physics, 2010-10-29) Alici, K. B.; Bilotti, F.; Vegni, L.; Özbay, Ekmel
We designed, implemented, and experimentally characterized electrically thin microwave absorbers by using the metamaterial concept. The absorbers consist of (i) a metal back plate and an artificial magnetic material layer; (ii) metamaterial back plate and a resistive sheet layer. We investigated absorber performance in terms of absorbance, fractional bandwidth, and electrical thickness, all of which depend on the dimensions of the metamaterial unit cell and the distance between the back plate and metamaterial layer. As a proof of concept, we demonstrated a λ/4.7 thick absorber of type I, with a 99.8% absorption peak along with a 8% fractional bandwidth. We have shown that as the electrical size of the metamaterial unit cell decreases, the absorber electrical thickness can further be reduced. We investigated this concept by using two different magnetic metamaterial inclusions: the split-ring resonator (SRR) and multiple SSR (MSRR). We have also demonstrated experimentally a λ/4.7 and a λ/4.2 thick absorbers of type II, based on SRR and MSRR magnetic metamaterial back plates, respectively. The absorption peak of the SRR layout is 97.4%, while for the MSRR one the absorption peak is 98.4%. The 10 dB bandwidths were 9.9% and 9.6% for the SRR and MSRR cases, respectively.
Open Access
Nanoantenna couplers for metal-insulator-metal waveguide interconnects
(SPIE, 2010) Onbasli, M.C.; Okyay, Ali Kemal
State-of-the-art copper interconnects suffer from increasing spatial power dissipation due to chip downscaling and RC delays reducing operation bandwidth. Wide bandwidth, minimized Ohmic loss, deep sub-wavelength confinement and high integration density are key features that make metal-insulator-metal waveguides (MIM) utilizing plasmonic modes attractive for applications in on-chip optical signal processing. Size-mismatch between two fundamental components (micron-size fibers and a few hundred nanometers wide waveguides) demands compact coupling methods for implementation of large scale on-chip optoelectronic device integration. Existing solutions use waveguide tapering, which requires more than 4λ-long taper distances. We demonstrate that nanoantennas can be integrated with MIM for enhancing coupling into MIM plasmonic modes. Two-dimensional finite-difference time domain simulations of antennawaveguide structures for TE and TM incident plane waves ranging from λ = 1300 to 1600 nm were done. The same MIM (100-nm-wide Ag/100-nm-wide SiO2/100-nm-wide Ag) was used for each case, while antenna dimensions were systematically varied. For nanoantennas disconnected from the MIM; field is strongly confined inside MIM-antenna gap region due to Fabry-Perot resonances. Major fraction of incident energy was not transferred into plasmonic modes. When the nanoantennas are connected to the MIM, stronger coupling is observed and E-field intensity at outer end of core is enhanced more than 70 times. © 2010 SPIE.
Open Access
Non-ideal cloaking based on Fabry-Perot resonances in single-layer high-index dielectric shells
(Optical Society of American (OSA), 2009) Serebryannikov, A.E.; Usik P.V.; Özbay, Ekmel
Strong reduction of the scattering cross section is obtained for subwavelength dielectric and conducting cylinders without any magnetism for both TE and TM polarizations. The suggested approach is based on the use of Fabry-Perot type radial resonances, which can appear in single-layer, high-ε, isotropic, and homogeneous shells with the properly chosen parameters. Frequencies of the minima of the scattering cross section, which are associated with the cloaking, typically depend on whether TE or TM polarization is considered. In some cases, large-positive-ε and largenegative-e objects can be cloaked. In other cases, non-ideal multifrequency cloaking can be realized. ©2009 Optical Society of America.
Open Access
Optically thin composite resonant absorber at the near-infrared band: A polarization independent and spectrally broadband configuration
(Optical Society of American (OSA), 2011) Boratay Alici, K.; Burak Turhan, A.; Soukoulis, C.M.; Özbay, Ekmel
We designed, fabricated, and experimentally characterized thin absorbers utilizing both electrical and magnetic impedance matching at the near-infrared regime. The absorbers consist of four main layers: a metal back plate, dielectric spacer, and two artificial layers. One of the artificial layers provides electrical resonance and the other one provides magnetic resonance yielding a polarization independent broadband perfect absorption. The structure response remains similar for the wide angle of incidence due to the sub-wavelength unit cell size of the constituting artificial layers. The design is useful for applications such as thermal photovoltaics, sensors, and camouflage. ©2011 Optical Society of America.
Open Access
Raman enhancement on a broadband meta-surface
(American Chemical Society, 2012-07-30) Ayas S.; Güner, H.; Türker, B.; Ekiz, O. O.; Dirisaglik, F.; Okyay, Ali Kemal; Dâna, A.
Plasmonic metamaterials allow confinement of light to deep subwavelength dimensions, while allowing for the tailoring of dispersion and electromagnetic mode density to enhance specific photonic properties. Optical resonances of plasmonic molecules have been extensively investigated; however, benefits of strong coupling of dimers have been overlooked. Here, we construct a plasmonic meta-surface through coupling of diatomic plasmonic molecules which contain a heavy and light meta-atom. Presence and coupling of two distinct types of localized modes in the plasmonic molecule allow formation and engineering of a rich band structure in a seemingly simple and common geometry, resulting in a broadband and quasi-omni-directional meta-surface. Surface-enhanced Raman scattering benefits from the simultaneous presence of plasmonic resonances at the excitation and scattering frequencies, and by proper design of the band structure to satisfy this condition, highly repeatable and spatially uniform Raman enhancement is demonstrated. On the basis of calculations of the field enhancement distribution within a unit cell, spatial uniformity of the enhancement at the nanoscale is discussed. Raman scattering constitutes an example of nonlinear optical processes, where the wavelength conversion during scattering may be viewed as a photonic transition between the bands of the meta-material.
Open Access
Single and cascaded, magnetically controllable metasurfaces as terahertz filters
(Optical Society of America OSA, 2016) Serebryannikov, A. E.; Lakhtakia, A.; Özbay, Ekmel
Transmission of a normally incident, linearly polarized, plane wave through either a single electrically thin metasurface comprising H-shaped subwavelength resonating elements made of magnetostatically controllable InAs or a cascade of several such metasurfaces was simulated in the terahertz regime. Stop bands that are either weakly or strongly controllable can be exhibited by a single metasurface by proper choice of the orientation of the magnetostatic field, and a ∼19%downshift of stop bands in the 0.1-5.5 THz spectral regime is possible on increasing the magnetostatic field strength from 0 to 1 T. Better controllability and wider bandwidths are possible by increasing the number of metasurfaces in a cascade, although increase of the total losses can lead to some restrictions. ON/OFF switching regimes, realizable either by applying/removing the magnetostatic field or just by changing its orientation, exist.