Photonics / Fotonik

Permanent URI for this collectionhttps://hdl.handle.net/11147/2590

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Author: search.filters.author.Kocabaş, ÇoşkunPublication Index: search.filters.publicationIndex.PubMed

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Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 84
    Citation - Scopus: 82
    Topological Engineering of Terahertz Light Using Electrically Tunable Exceptional Point Singularities
    (American Association for the Advancement of Science, 2022) Ergöktaş, M. Said; Soleymani, Sina; Kakenov, Nurbek; Wang, Kaiyuan; Smith, Thomas B.; Bakan, Gökhan; Balcı, Sinan; Principi, Alessandro; Novoselov, Kostya S.; Özdemir, Şahin K.; Kocabaş, Çoşkun
    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 emergence of EPs in an electrically controlled interaction between light and a collection of organic molecules in the terahertz regime at room temperature. We show that the intensity and phase of terahertz pulses can be controlled by a gate voltage, which drives the device across the EP. Our electrically tunable system allows reconstruction of the Riemann surface associated with the complex energy landscape and provides topological control of light by tuning the loss imbalance and frequency detuning of interacting modes. Our approach provides a platform for developing topological optoelectronics and studying the manifestations of EP physics in light-matter interactions.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 19
    Strong Coupling of Carbon Quantum Dots in Liquid Crystals
    (American Chemical Society, 2022) Sarısözen, Sema; Polat, Nahit; Mert Balcı, Fadime; Güvenç, Çetin Meriç; Kocabaş, Çoşkun; Yağlıoğlu, Halime Gül; Balcı, Sinan
    Carbon quantum dots (CDs) have recently received a tremendous amount of interest owing to their attractive optical properties. However, CDs have broad absorption and emission spectra limiting their application ranges. We herein, for the first time, show synthesis of water-soluble red emissive CDs with a very narrow line width (∼75 meV) spectral absorbance and hence demonstrate strong coupling of CDs and plasmon polaritons in liquid crystalline mesophases. The excited state dynamics of CDs has been studied by ultrafast transient absorption spectroscopy, and CDs display very stable and strong photoluminescence emission with a quantum yield of 35.4% and a lifetime of ∼2 ns. More importantly, we compare J-aggregate dyes with CDs in terms of their absorption line width, photostability, and ability to do strong coupling, and we conclude that highly fluorescent CDs have a bright future in the mixed light-matter states for emerging applications in future quantum technologies.
  • Article
    Citation - WoS: 134
    Citation - Scopus: 136
    Electrically Switchable Metadevices Via Graphene
    (American Association for the Advancement of Science, 2018) Balcı, Osman; Kakenov, Nurbek; Karademir, Ertuğrul; Balcı, Sinan; Çakmakyapan, Semih; Polat, Emre O.; Çağlayan, Hümeyra; Özbay, Ekmel; Kocabaş, Çoşkun
    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 reconfigurable components operating over a broad spectrum with a wide dynamic range. However, the existing capability of metamaterials is not sufficient to realize this goal. By integrating passive metamaterials with active graphene devices, we demonstrate a new class of electrically controlled active metadevices working in microwave frequencies. The fabricated active metadevices enable efficient control of both amplitude (>50 dB) and phase (>90°) of electromagnetic waves. In this hybrid system, graphene operates as a tunable Drude metal that controls the radiation of the passive metamaterials. Furthermore, by integrating individually addressable arrays of metadevices, we demonstrate a new class of spatially varying digital metasurfaces where the local dielectric constant can be reconfigured with applied bias voltages. In addition, we reconfigure resonance frequency of split-ring resonators without changing its amplitude by damping one of the two coupled metasurfaces via graphene. Our approach is general enough to implement various metamaterial systems that could yield new applications ranging from electrically switchable cloaking devices to adaptive camouflage systems.