Browsing by Author "Kakenov, Nurbek"

Now showing items 1-16 of 16

    • Broadband THz modulators based on multilayer graphene on PVC 

      Kaya, E.; Kakenov, Nurbek; Kocabaş, Coşkun; Altan, H.; Esentürk, O. (IEEE, 2016)
      In this study we present the direct terahertz time-domain spectroscopic measurement of CVD-grown multilayer graphene (MLG) on PVC substrate with an electrically tunable Fermi level. In a configuration consisting MLG and ...

    • Compressive sensing imaging with a graphene modulator at THz frequency in transmission mode 

      Özkan, V. A.; Takan, T.; Kakenov, Nurbek; Kocabaş, Coşkun; Altan, H. (IEEE, 2016)
      In this study we demonstrate compressive sensing imaging with a unique graphene based optoelectronic device which allows us to modulate the THz field through an array of columns or rows distributed throughout its face.

    • Controlling phase of microwaves with active graphene surfaces 

      Balcı, Osman; Kakenov, Nurbek; Kocabaş, Coşkun (American Institute of Physics Inc., 2017)
      In this letter, we report a method to control the reflection phase of microwaves using electrically tunable graphene devices. The device consists of mutually gated large-area graphene layers placed at a quarter-wave distance ...

    • Electrically controlled terahertz spatial light modulators with graphene arrays 

      Kakenov, Nurbek; Takan, T.; Özkan, V. A.; Balcı, Osman; Polat, Emre Ozan; Altan, H.; Kocabaş, Coşkun (IEEE, 2016)
      Gate-tunable high-mobility electrons on atomically thin graphene layers provide a unique opportunity to control electromagnetic waves in a very broad spectrum. In this paper, we describe an electrically-controlled multipixel ...

    • Electrically switchable metadevices via graphene 

      Balcı, Osman; Kakenov, Nurbek; Karademir, E.; Balcı, S.; Çakmakyapan, S.; Polat, E. O.; Cağlayan, H.; Özbay, Ekmel; Kocabaş, Coşkun (American Association for the Advancement of Science, 2018)
      Metamaterials bring subwavelength resonating structures together to overcome the limitations of conventional materials. The realization of active metadevices has been an outstanding challenge that requires electrically ...

    • Femtosecond pulse generation from a Ti3+: Sapphire laser near 800 nm with voltage reconfigurable graphene saturable absorbers 

      Baylam, Işınsu; Özharar, Sarper; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroglu, Alphan (OSA - The Optical Society, 2017)
      We experimentally show that a voltage-controlled graphene-gold supercapacitor saturable absorber (VCG-gold-SA) can be operated as a fast saturable absorber with adjustable linear absorption at wavelengths as low as 795 nm. ...

    • Graphene mode-locked diode-pumped Cr:LiSAF laser at 857 nm 

      Canbaz, F.; Kakenov, Nurbek; Kocabaş, Coşkun; Demirbaş, U.; Sennaroglu, A. (IEEE, 2015)
      The Cr:LiSAF gain medium, belonging to the class of Cr:colquiirite lasers, possesses a broad gain bandwidth suitable for the generation of femtosecond pulses near 850 nm [1]. Because the nonlinear refractive index of these ...

    • Graphene-Based Adaptive Thermal Camouflage 

      Salihoğlu, Ömer; Uzlu, H. B.; Yakar, Ozan; Aas, Shahnaz; Balci, Osman; Kakenov, Nurbek; Balci, S.; Olcum, S.; Süzer, Şefik; Kocabas, Coşkun (American Chemical Society, 2018)
      In nature, adaptive coloration has been effectively utilized for concealment and signaling. Various biological mechanisms have evolved to tune the reflectivity for visible and ultraviolet light. These examples inspire many ...

    • Graphene-based electrically tunable terahertz optoelectronics 

      Kakenov, Nurbek (Bilkent University, 2016-09)
      Advances in terahertz (THz) research and technology, has bridged the gap between radio-frequency electronics and optics. More efficient control of THz waves would highly benefit noninvasive, high-resolution imaging ...

    • Graphene-gold supercapacitor as a voltage-controlled saturable absorber for femtosecond pulse generation 

      Baylam, I.; Balcı, Osman; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A. (OSA, 2015)
      We report, for the first time to our knowledge, a voltage-controlled graphene-gold supercapacitor saturable absorber, as a modulator with adjustable insertion loss for low-gain mode-locked lasers. Nearly transform-limited, ...

    • Investigation of the ultrafast response and saturable absorption of voltage-controlled graphene 

      Baylam, I.; Çizmeciyan, M. N.; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A. (OSA, 2018)
      Ultrafast pump-probe measurements show that at a bias voltage of 1V, voltage reconfigurable graphene supercapacitors can operate as fast saturable absorbers with adjustable insertion loss over an ultrabroad spectral range ...

    • Modulation behaviors, conductivities, and carrier dynamics of single and multilayer graphenes 

      Kaya, E.; Kakenov, Nurbek; Kocabaş, Coşkun; Altan, H.; Esentürk, O. (IEEE Computer Society, 2019)
      Time domain and time resolved terahertz studies of single- and multi-layer graphene (SLG and MLG) samples and modulator devices will be presented. A high performance up to 100% of modulators were observed with the devices ...

    • Probing interfacial processes on carbon nanotubes and graphene surfaces 

      Kakenov, Nurbek (Bilkent University, 2012)
      The surface of low-dimensional carbon (carbon nanotubes and graphene) has unique electronic properties due to the delocalized p-orbitals. Very high carrier mobility with nanoscale dimension make carbon nanotubes and ...

    • Synthesis of graphene on ultra-smooth copper foils for large area flexible electronics 

      Polat, E. O.; Balcı, Osman; Kakenov, Nurbek; Kocabaş, Coşkun; Dahiya, R. (IEEE, 2015)
      This work demonstrates the synthesis of high quality, single layer graphene on commercially available ultra-smooth copper foils. The presented method will result in improved scalability of graphene based electronic and ...

    • Topological engineering of terahertz light using electrically tunable exceptional point singularities 

      Ergoktas, M. Said; Soleymani, Sina; Kakenov, Nurbek; Wang, Kaiyuan; Smith, Thomas B.; Bakan, Gokhan; Balci, Sinan; Principi, Alessandro; Novoselov, Kostya S.; Ozdemir, Sahin K.; Kocabas, Coskun (American Association for the Advancement of Science (AAAS), 2022)
      The topological structure associated with the branch point singularity around an exceptional point (EP) can provide tools for controlling the propagation of light. Through use of graphene-based devices, we demonstrate the ...

    • Ultrafast spectroscopy of voltage reconfigurable graphene saturable absorbers in the visible and near infrared 

      Baylam, I.; Kakenov, Nurbek; Kocabaş, Coşkun; Sennaroğlu, A.; Çizmeciyan, M. N. (IOP, 2019-04-23)
      We describe a detailed experimental investigation of the ultrafast nonlinear response of a voltagecontrolled graphene-gold saturable absorber (VCG-gold-SA) by employing femtosecond pump probe spectroscopy. Visible and ...