Now showing items 1-20 of 46

    • Beaming and enhanced transmission through a subwavelength aperture via epsilon-near-zero media 

      Hajian, H.; Özbay, Ekmel; Caglayan, H. (Nature Publishing Group, 2017)
      We numerically validate and experimentally realize considerable funneling of electromagnetic energy through a subwavelength aperture that is covered with an epsilon-near-zero metamaterial (ENZ). The epsilon-near-zero ...
    • Beaming of electromagnetic waves emitted through a subwavelength annular aperture 

      Caglayan, H.; Bulu, I.; Özbay, Ekmel (Optical Society of American (OSA), 2006)
      We study the diffraction of electromagnetic waves from subwavelength metallic circular apertures in the microwave spectrum. The theoretical and experimental demonstration of the near- and far-field electromagnetic distributions ...
    • Beaming of light and enhanced transmission via surface modes of photonic crystals 

      Bulu, I.; Caglayan, H.; Özbay, Ekmel (Optical Society of America, 2005-11-15)
      We report beaming and enhanced transmission of electromagnetic waves by use of surface corrugated photonic crystals. The modes of a finite-size photonic crystal composed of dielectric rods in free space have been analyzed ...
    • Bright off-axis directional emission with plasmonic corrugations 

      Sattari, H.; Rashed, A. R.; Özbay, Ekmel; Caglayan, H. (OSA - The Optical Society, 2017)
      In this work, a new plasmonic bulls-eye structure is introduced to efficiently harvest the emitted light from diamond nitrogen vacancy (NV) centers. We show that the presence of a simple metal sub-layer underneath of a ...
    • Cavity formation in split ring resonators 

      Caglayan, H.; Bulu, I.; Loncar, M.; Özbay, Ekmel (Elsevier BV, 2008-12)
      We report that it is possible to obtain a cavity structure by the deformation of a unit cell of an split ring resonator (SRR) structure. We presented the Q-factor of the cavity resonance as 192 for an SRR-based single ...
    • Chiral metamaterials with negative refractive index based on four "U" split ring resonators 

      Li, Z.; Zhao, R.; Koschny, T.; Kafesaki, M.; Alici, K. B.; Colak, E.; Caglayan, H.; Özbay, Ekmel; Soukoulis, C. M. (American Institute of Physics, 2010-08-23)
      A uniaxial chiral metamaterial is constructed by double-layered four "U" split ring resonators mutually twisted by 90°. It shows a giant optical activity and circular dichroism. The retrieval results reveal that a negative ...
    • Compact size highly directive antennas based on the SRR metamaterial medium 

      Bulu, I.; Caglayan, H.; Aydin, K.; Özbay, Ekmel (Institute of Physics Publishing, 2005)
      In this work, we studied the far-field properties of the microwave radiation from sources embedded inside the split-ring resonator (SRR) metamaterial medium. Our results showed that the emitted power near the resonance ...
    • Comparison of back and top gating schemes with tunable graphene fractal metasurfaces 

      Aygar, A. M.; Balci, O.; Cakmakyapan, S.; Kocabas, C.; Caglayan, H.; Özbay, Ekmel (American Chemical Society, 2016)
      In this work, fractal metasurfaces that consist of periodic gold squares on graphene are used to increase light-graphene interaction. We show by simulations and experiments that higher level fractal structures result in ...
    • Composite chiral metamaterials with negative refractive index and high values of the figure of merit 

      Li, Z.; Caglayan, H.; Alici, K. B.; Kafesaki, M.; Soukoulis, C. M.; Özbay, Ekmel (Optical Society of America, 2012)
      A composite chiral metamaterial (CCMM) is designed and studied both numerically and experimentally. The CCMM is constructed by the combination of a continuous metallic wires structure and a purely chiral metamaterial (CMM) ...
    • Coupling effect between two adjacent chiral structure layers 

      Li, Z.; Caglayan, H.; Colak, E.; Zhou, J.; Soukoulis, C. M.; Özbay, Ekmel (Optical Society of America, 2010-03-01)
      A pair of mutually twisted metallic cross-wires can produce giant optical activity. When this single chiral layer is stacked layer by layer in order to build a thick chiral metamaterial, strong coupling effects are ...
    • Coupling enhancement of split ring resonators on graphene 

      Cakmakyapan, S.; Caglayan, H.; Özbay, Ekmel (Pergamon Press, 2014-12)
      Metallic split ring resonator (SRR) structures are used in nanophotonics applications in order to localize and enhance incident electromagnetic field. Electrically controllable sheet carrier concentration of graphene ...
    • Enhanced transmission and beaming via a zero-index photonic crystal 

      Hajian, H.; Özbay, Ekmel; Caglayan, H. (American Institute of Physics Inc., 2016)
      Certain types of photonic crystals with Dirac cones at the Γ point of their band structure have a zero effective index of refraction at Dirac cone frequency. Here, by an appropriate design of the photonic structure, we ...
    • Enhanced transmission and directivity from metallic subwavelength apertures with nonuniform and nonperiodic grooves 

      Li, Z.; Caglayan, H.; Colak, E.; Özbay, Ekmel (AIP Publishing LLC, 2008)
      Nonuniform and nonperiodic grooves are used to enhance the transmission and directivity of emissions from a single metallic subwavelength aperture. By using nonuniform and nonperiodic grooves, the amplitude and phase of ...
    • Enhanced tunability of V-shaped plasmonic structures using ionic liquid gating and graphene 

      Ozdemir, O.; Aygar, A. M.; Balci, O.; Kocabas, C.; Caglayan, H.; Özbay, Ekmel (Elsevier Ltd, 2016)
      Graphene is a strong candidate for active optoelectronic devices because of its electrostatically tunable optical response. Current substrate back-gating methods are unable to sustain high fields through graphene unless a ...
    • Experimental demonstration of labyrinth-based left-handed metamaterials 

      Bulu, I.; Caglayan, H.; Özbay, Ekmel (Optical Society of America, 2005-12-12)
      In this present work, we propose and demonstrate a resonant structure that solves two major problems related to the split-ring resonator structure. One of the problems related to the split-ring resonator structure is the ...
    • Experimental observation of subwavelength localization using metamaterial-based cavities 

      Caglayan, H.; Bulu, I.; Loncar, M.; Özbay, Ekmel (Optical Society of America, 2009-01-01)
      We report subwavelength localization of electromagnetic fields within cavities based on metamaterials. Cavity resonances are observed in the transmission spectrum of a split-ring resonator and composite metamaterials cavity ...
    • Experimental validation of strong directional selectivity in nonsymmetric metallic gratings with a subwavelength slit 

      Cakmakyapan, S.; Caglayan, H.; Serebryannikov, A. E.; Özbay, Ekmel (American Institute of Physics, 2011-02-02)
      Strong directional selectivity is theoretically predicted and experimentally validated at the microwave frequencies in the beaming regime for a single subwavelength slit in nonsymmetric metallic gratings with double-side ...
    • Extraordinary grating-coupled microwave transmission through a subwavelength annular aperture 

      Caglayan, H.; Bulu, I.; Özbay, Ekmel (Optical Society of America, 2005-03-07)
      We studied coupling phenomena between surface plasmons and electromagnetic waves in the microwave spectrum using circular apertures surrounded by array of grooves. We first present experimental and theoretical results of ...
    • The focusing effect of graded index photonic crystals 

      Kurt, H.; Colak, E.; Cakmak, O.; Caglayan, H.; Özbay, Ekmel (AIP Publishing LLC, 2008)
      We describe an approach to implement graded index (GRIN) structures using two-dimensional photonic crystals (PCs). The lattice spacing along the transverse direction to propagation is altered and we show, both theoretically ...
    • Focusing surface plasmons via changing the incident angle 

      Caglayan, H.; Bulu, I.; Özbay, Ekmel (AIP Publishing LLC, 2008)
      We report a circular metallic aperture with a subwavelength circular slit in the microwave regime, in which we experimentally demonstrate that this aperture can excite and focus surface plasmons. Under normal illumination, ...