Now showing items 1-20 of 24

    • AlGaN quadruple-band photodetectors 

      Gökkavas, Mutlu; Bütün, Serkan; Caban, P.; Strupinski, W.; Özbay, Ekmel (IEEE, 2009)
      Quadruple back-illuminated ultraviolet metal-semiconductor-metal photodetectors with four different spectral responsivity bands were demonstrated. The average of the full-width at half-maximum (FWHM) of the quantum efficiency ...
    • Atomistic structure simulation of silicon nanocrystals driven with suboxide penalty energies 

      Yılmaz, Dündar E.; Bulutay, Ceyhun; Çağın, T. (American Scientific Publishers, 2008)
      The structural control of silicon nanocrystals embedded in amorphous oxide is currently an important technological problem. In this work, an approach is presented to simulate the structural behavior of silicon nanocrystals ...
    • Broadband absorption enhancement in an uncooled microbolometer infrared detector 

      Kebapcı, B.; Dervişoğlu, Ö.; Battal, Enes; Okyay, Ali Kemal; Akın, T. (SPIE, 2014)
      This paper introduces a method for a broadband absorption enhancement in the LWIR range (8-12 μm), in single layer microbolometer pixels with 35 μm pitch. For the first time in the literature, this study introduces a very ...
    • Broadband one way propagation via dielectric waveguides with unequal effective index 

      Öner, B. B.; Üstün, K.; Kurt, H.; Okyay, Ali Kemal; Turhan-Sayan, G. (IEEE, 2014)
      We present an efficient approach for broad band one way propagation of light by parallel and unequal dielectric waveguides leading different effective phase shifts. Three dimensional numerical simulations show that 30% ...
    • CdSe/ZnS core-shell nanocrystal based scintillators for enhanced detection in UV 

      Demir, Hilmi Volkan; Soğancı, İbrahim Murat; Mutlugün, Evren (IEEE, 2006)
      In this work, we present a novel scintillator that incorporates CdSe/ZnS core-shell nanocrystals to utilize both their high quantum fluorescence efficiency in the visible and high optical absorption in the UV for the purpose ...
    • Experimental and theoretical investigations of electronic and atomic structure of Si-nanocrystals formed in sapphire by ion implantation 

      Wainstein, D.; Kovalev, A.; Tetelbaum, D.; Mikhailov, A.; Bulutay, Ceyhun; Aydınlı, Atilla (IOP, 2008)
      The semiconductor nanocomposites based on Si nanocrystals in dielectric matrices attract a great amount of attention due to their ability for luminescence in visible and near-IR part of the electromagnetic spectrum. Si ...
    • Experimental observation of true left-handed metamaterial 

      Aydın, Koray; Güven, Kaan; Özbay, Ekmel (IEEE, 2005)
      We report a true left-handed (LH) behavior in composite metamaterials. The magnetic resonance of the SRR structure is demonstrated. Plasma frequency of the LH material is shown to be lower than that of the wires.
    • Ferroelectric based tuneable SRR based metamaterial for microwave applications 

      Özbay, Ekmel; Aydın, Koray; Bütün, Serkan; Kolodziejak, K.; Pawlak, D. (IEEE, 2007)
      We discuss the possibility of achieving tunable split ring resonators at microwave frequencies. One method is to use varying capacitance values to tune the magnetic resonance frequency. As another method ferroelectric thin ...
    • InGaN/GaN based LEDs with electroluminescence in violet, blue, and green tuned by epitaxial growth temperature 

      Sarı, Emre; Nizamoğlu, Sedat; Özel, Tuncay; Demir, Hilmi Volkan; İnal, Ayşe; Ülker, Erkin; Özbay, Ekmel; Dikme, Y.; Heuken, M. (IEEE, 2007)
      In this work, we present a full set of InGaN LEDs based on a single optimal InGaN/GaN quantum design with emission wavelengths spanning from green to blue to violet by tuning the active layer growth temperature to precisely ...
    • Labyrinth based left-handed metamaterials and sub-wavelength focusing of electromagnetic waves 

      Özbay, Ekmel; Bulu, İrfan; Çağlayan, Hümeyra (SPIE, 2006)
      We propose and demonstrate a resonant structure that solves two major problems related to the split-ring resonator structure. These major problems may be stated as the bianisotropy and electric coupling to the magnetic ...
    • Localized plasmon-engineered spontaneous emission of CdSe/ZnS nanocrystals closely-packed in the proximity of Ag nanoislands 

      Soğancı, İbrahim Murat; Nizamoğlu, Sedat; Mutlugün, Evren; Demir, Hilmi Volkan (2007)
      As a proof-of-concept demonstration, we show that the localized plasmons of metal nanoisland films provide the ability to modify and control the collective spontaneous emission of nanocrystals in their proximity (including ...
    • The magical world of metamaterials 

      Çağlayan, Hümeyra; Özbay, Ekmel (SPIE, 2009)
      We review experimental and theoretical studies performed on left-handed metamaterials (LHM). The metamaterials exhibit quiet unusual electromagnetic properties such as negative refraction, negative phase velocity, subwavelength ...
    • Nanocrystal hybridized white light sources integrated on near UV leds 

      Nizamoğlu, Sedat; Demir, Hilmi Volkan (World Scientific Publishing, 2007)
      We report on CdSe/ZnS core-shell nanocrystal (NC) based white light sources integrated on near-UV InGaN/GaN light emitting diodes (LEDs). We present the design, epitaxial growth, fabrication, integration and characterization ...
    • Negative refraction and focusing of electromagnetic waves by photonic crystals 

      Bulu, İrfan; Çağlayan, Hümeyra; Özbay, Ekmel (IOP, 2006)
      In this work, we study the negative refraction and focusing effect by a metallodielectric photonic crystal. We show that by using a metallodielectric photonic crystal it is possible to obtain negative refraction for large ...
    • Nonlinearity management: from fiber oscillators to amplifiers 

      İlday, Fatih Ömer; Şenel, Ç.; Hamid, R.; Teamir, Tesfay G.; Pavlov, Ihor; Teğin, Uğur; Ergeçen, E.; Elahi, Parviz; Iegorov, R. (IEEE, 2016)
      While the standard approach to performance scaling in fiber lasers seeks to reduce nonlinear effects through chirping or mode scaling, I will review recent progress in a complementary approach, whereby the governing dynamics ...
    • Plasmonic nano-bio sensors for detection of E-coli bacteria 

      Cinel, Neval A.; Bütün, Serkan; Çalışkan, Deniz; Özbay, Ekmel (IEEE, 2009)
      Biological sensors, that rely on localized surface plasmon resonance exhibited by metallic nanocylinders fabricated using electron beam lithography and functionalized with the immobilization of biotin conjugated E-coli ...
    • Plasmonic structures with highly directional beaming properties 

      Çağlayan, Hümeyra; Bulu, İrfan; Özbay, Ekmel (IOP, 2006)
      We studied the diffraction of electromagnetic waves from subwavelength metallic circular apertures in the microwave spectrum. The metallic samples had a subwavelength hole with a diameter of 8 mm and had concentric grooves ...
    • Raman and TEM studies of Ge nanocrystal formation in SiOx: Ge/SiOx multilayers 

      Dana, Aykutlu; Aǧan, S.; Tokay, S.; Aydınlı, Atilla; Finstad, T. G. (Wiley, 2007)
      Alternating germanosilicate-siliconoxide layers of 10-30 nm thickness were grown on Si substrates by plasma enhanced chemically vapor deposition (PECVD). The compositions of the grown films were determined by X-ray ...
    • Review of experimental studies on microwave left-handed metamaterials 

      Özbay, Ekmel; Aydın, Koray (American Institute of Physics, 2007)
      We review experimental studies on left-handed metamaterials operating at microwave frequencies. Left-handed transmission is obtained from a composite metamaterial consisting of periodic split ring resonator and wire arrays. ...
    • SbSI based photonic crystal superlattices: band structure and optics 

      Şimsek, Ş.; Koç, H.; Palaz, S.; Oltulu, O.; Mamedov, Amirullah M.; Özbay, Ekmel (IOP, 2015)
      In this work, we present an investigation of the optical properties and band structure calculations for the photonic crystal structures (PCs) based on one-dimensional (1D)-photonic crystal. Here we use 1D SbSI based layers ...