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Department: search.filters.department.Department of PhysicsSubject: search.filters.subject.Nanotechnology

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Now showing 1 - 10 of 21
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    Aerogels for optofluidic waveguides
    (MDPI, 2017) Jonas, Alexandr; N/A; Department of Physics; Department of Chemical and Biological Engineering; Özbakır, Yaprak; Erkey, Can; Kiraz, Alper; PhD Student; Faculty Member; Faculty Member; Department of Physics; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; 29633; 22542
    Aerogels-solid materials keeping their internal structure of interconnected submicron-sized pores intact upon exchanging the pore liquid with a gas-were first synthesized in 1932 by Samuel Kistler. Overall, an aerogel is a special form of a highly porous material with a very low solid density and it is composed of individual nano-sized particles or fibers that are connected to form a three-dimensional network. The unique properties of these materials, such as open pores and high surface areas, are attributed to their high porosity and irregular solid structure, which can be tuned through proper selection of the preparation conditions. Moreover, their low refractive index makes them a remarkable solid-cladding material for developing liquid-core optofluidic waveguides based on total internal reflection of light. This paper is a comprehensive review of the literature on the use of aerogels for optofluidic waveguide applications. First, an overview of different types of aerogels and their physicochemical properties is presented. Subsequently, possible techniques to fabricate channels in aerogel monoliths are discussed and methods to make the channel surfaces hydrophobic are described in detail. Studies in the literature on the characterization of light propagation in liquid-filled channels within aerogel monoliths as well as their light-guiding characteristics are discussed. Finally, possible applications of aerogel-based optofluidic waveguides are described.
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    An LED-based super resolution GPU implemented structured illumination microscope
    (Spie-Int Soc Optical Engineering, 2020) Aydin, Musa; N/A; N/A; N/A; Department of Physics; Uysallı, Yiğit; Özgönül, Ekin; Morova, Berna; Kiraz, Alper; PhD Student; PhD Student; Researcher; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; College of Sciences; N/A; N/A; N/A; 22542
    Fluorescence imaging of sub-cellular structures with sizes below the diffraction limit is vital in understanding cellular processes. Relying on exciting the sample with different illumination patterns and image processing for the elimination of background fluorescence, Structured Illumination Microscopy (SIM) provides imaging capability beyond diffraction limit using relatively simple optical setups. Here, we present a laser-free, DLP projector-based, and GPU-implemented SIM super resolution microscope. Sub-diffractive biological structures were imaged with a lateral resolution of similar to 150 nm. The microscopy system is LED-based and entirely home-built which enables customizable operation at a low cost.
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    Erratum to: exciton recycling via InP quantum dot funnels for luminescent solar concentrators
    (Tsinghua University) Ow-Yang, Cleva W.; N/A; N/A; N/A; N/A; Department of Physics; Department of Electrical and Electronics Engineering; Jalali, Houman Bahmani; Sadeghi, Sadra; Toker, Işınsu Baylam; Han, Mertcan; Sennaroğlu, Alphan; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Physics; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; N/A; N/A; 23851; 130295
    The article "Exciton recycling via InP quantum dot funnels for luminescent solar concentrators" written by Houman Bahmani Jalali(1),, Sadra Sadeghi(2),, Isinsu Baylam(3,4), Mertcan Han(5), Cleva W. Ow-Yang(6), Alphan Sennaroğlu(3,4), and Sedat Nizamoğlu(1,2,5) (x2709;), was originally published Online First without Open Access. After publication online first, the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to (c) The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The original article has been corrected.
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    Fabrication of ZnO nanowires and nanorods
    (Elsevier, 2012) Öztürk, Sadullah; Kılınç, Necmettin; Öztürk, Zafer Ziya; Department of Physics; Taşaltın, Nevin; Researcher; Department of Physics; College of Sciences; 220956
    In this study, we focused on the fabrication of two types of ZnO nanostructures, nanorods and nanowires, using different techniques. ZnO nanowires were fabricated by cathodically induced sol-gel electrodeposition using an anodic aluminum oxide (AAO) template. ZnO nanowires were approximately 65 nm in diameter and 10 mu m in length. Also, ZnO nanorods were fabricated by a hydrothermal technique using ZnO seed layer coated glass substrate. ZnO nanorods were approximately 30 nm in diameter and 1 mu m in length. Obtained vertical aligned ZnO nanowires and nanorods were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and UV-vis spectrophotometry.
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    Fluorescence excitation by enhanced plasmon upconversion under continuous wave illumination
    (Elsevier, 2016) Taşgın, Mehmet Emre; Salakhutdinov, Ildar; Kendziora, Dania; Abak, Musa Kurtulus; Piantanida, Luca; Fruk, Ljiljana; Lazzarino, Marco; Bek, Alpan; Department of Physics; Türkpençe, Deniz; Researcher; Department of Physics; College of Sciences; N/A
    We demonstrate effective background-free continuous wave nonlinear optical excitation of molecules that are sandwiched between asymmetrically constructed plasmonic gold nanoparticle clusters. We observe that near infrared photons are converted to visible photons through efficient plasmonic second harmonic generation. Our theoretical model and simulations demonstrate that Fano resonances may be responsible for being able to observe nonlinear conversion using a continuous wave light source. We show that nonlinearity enhancement of plasmonic nanostructures via coupled quantum mechanical oscillators such as molecules can be several orders larger as compared to their classical counterparts.
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    Guiding of emulsion droplets in microfluidic chips along shallow tracks defined by laser ablation
    (Springer Heidelberg, 2017) Coskun, Umut Can; Morova, Yagiz; Bozkurt, Asuman Asikoglu; Jonas, Alexandr; Akturk, Selcuk; N/A; Department of Physics; Department of Physics; Rashid, Muhammed Zeeshan; Erten, Ahmet Can; Kiraz, Alper; PhD Student; Teaching Faculty; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; 233923; 22542
    We demonstrate controlled guiding of nanoliter emulsion droplets of polar liquids suspended in oil along shallow hydrophilic tracks fabricated at the base of microchannels located within microfluidic chips. The tracks for droplet guiding are generated by exposing the glass surface of polydimethylsiloxane (PDMS)-coated microscope slides via femtosecond laser ablation. The difference in wettability of glass and PDMS surfaces together with the shallow steplike transverse topographical profile of the ablated tracks allows polar droplets wetting preferentially the glass surface to follow the track. In this study, we investigate guiding of droplets of two different polar liquids (water/ethylene glycol) with and without surfactant suspended in an oil medium along surface tracks of different depths of 1, 1.5, and 2 mu m. The results of experiments are also verified with computational fluid dynamics simulations. Guiding of droplets along the tracks as a function of the droplet composition and size and the surface profile depth is evaluated by analyzing the trajectories of moving droplets with respect to the track central axis, and conditions for stable guiding are identified. The experiments and numerical simulations indicate that while the track topography plays a role in droplet guiding using 1.5-and 2-mu m deep tracks, for the case of the smallest track depth of 1 ae m, droplet guiding is mainly caused by surface energy modification along the track rather than the presence of a topographical step on the surface. Our results can be exploited to sort passively different microdroplets mixed in the same microfluidic chip, based on their inherent wetting properties, and they can also pave the way for guiding of droplets along reconfigurable tracks defined by surface energy modifications obtained using other external control mechanisms such as electric field or light.
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    Modification and dynamics inside diamond by femtosecond laser double-pulse irradiation
    (Japan Laser Processing Soc, 2016) Sakakura, Masaaki; Okada, Takuro; Bharadwaj, Vibhav; Sotillo, Belen; Eaton, Shane M.; Ramponi, Roberta; Shimotsuma, Yasuhiko; Miura, Kiyotaka; Department of Physics; N/A; Serpengüzel, Ali; Gökay, Ulaş Sabahattin; Faculty Member; N/A; Department of Physics; College of Sciences; N/A; 27855; N/A
    We investigated modifications and the temporal evolution of the morphology in the photoexcited region inside diamond single crystal after photoexcitation by tightly focused fs laser pulses. We found that double-pulse irradiation with 200-400 fs laser pulses was able to induce a permanent modification in the photoexcited region, while single-pulse irradiation with 100-300 fs laser pulses was not. The modification by double-pulse irradiation became larger for a longer time-difference between the two pulses in the range from 1 ps to 10 ps. The morphology change observed by a pump-probe optical microscope showed that the photoexcited region by double-pulse irradiation was smaller than by single-pulse irradiation, even for the same total pulse energy, with the amplitudes of the laser induced-stress waves being the same. This observation suggests that the photoinduced plasmas by double-pulse irradiation was localized in a smaller region than that by single-pulse irradiation, and the difference in plasma distribution could be the origin of the permanent modification.
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    Nanoscale plasmonic devices for dynamically controllable beam focusing and scanning
    (Elsevier, 2010) Çetin, Arif Engin; Department of Physics; Department of Physics; Sennaroğlu, Alphan; Müstecaplıoğlu, Özgür Esat; Faculty Member; Faculty Member; Department of Physics; College of Sciences; College of Sciences; 23851; 1674
    We have performed simulations to investigate the variable focusing and scanning capability of metallic nano-slit configurations. In a symmetric nanorod configuration inside an aperture with adjustable offset of the center rod, the focal position is found to be variable in the 0.5-3.5 mu m range. In a ladder configuration of the rods, the transmitted beam is found to be deflected up to 23 degrees. Horizontal displacement of rods allows for finer control of angular scanning up to 4 degrees. Such slit geometries offer the potential to be controlled by using nano-positioning systems for applications in dynamic beam shaping and scanning on the nanoscale.
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    Optically transportable optofluidic microlasers with liquid crystal cavities tuned by the electric field
    (Amer Chemical Soc, 2021) Jonas, Alexandr; Pilat, Zdenek; Jezek, Jan; Bernatova, Silvie; Jedlicka, Petr; Zemanek, Pavel; Department of Physics; N/A; Kiraz, Alper; Aas, Mehdi; Faculty Member; PhD Student; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 22542
    Liquid crystal microdroplets with readily adjustable optical properties have attracted considerable attention for building reconfigurable optofluidic microsystems for sensing, imaging, and light routing applications. In this quest, development of active optical microcavities serving as versatile integrated sources of coherent light and ultra-sensitive environmental sensors has played a prominent role. Here, we study transportable optofluidic microlasers reversibly tunable by an external electric field, which are based on fluorophore-doped emulsion droplets of radial nematic liquid crystals manipulated by optical tweezers in microfluidic chips with embedded liquid electrodes. Full transparency of the electrodes formed by a concentrated electrolyte solution allows for applying an electric field to the optically trapped droplets without undesired heating caused by light absorption. Taking advantage of independent, precise control over the electric and thermal stimulation of the lasing liquid crystal droplets, we characterize their spectral tuning response at various optical trapping powers and study their relaxation upon a sudden decrease in the trapping power. Finally, we demonstrate that sufficiently strong applied electric fields can induce fully reversible phase transitions in the trapped droplets even below the bulk melting temperature of the used liquid crystal. Our observations indicate viability of creating electrically tunable, optically transported microlasers that can be prepared on-demand and operated within microfluidic chips to implement integrated microphotonic or sensing systems.
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    Optofluidic lasers with aqueous quantum dots
    (Amer Chemical Soc, 2015) Chen, Qiushu; Fan, Xudong; Department of Physics; Kiraz, Alper; Faculty Member; Department of Physics; College of Sciences; 22542
    We achieved two types of laser emissions from aqueous quantum dots (Qps) using the same high-Q:factor optofluidic ring resonator (OFRR) platform. In the first type, 2 mu M QDs were in bulk buffer solution that filled the entire OFRR cavity volume. The lasing threshold was 0.1 mu J/mm(2), over 3 orders of magnitude lower than the state-of-the-art. In the second type of laser, the QDs were immobilized as a single layer on the interface between the OFRR inner wall and buffer solution with a surface density as low as 3 X 10(9)-10(10) cm(-2). The lasing threshold of 60 mu J/mm(2) was achieved. In both bulk solution and single-layer lasing cases, the laser emission persisted even under 5-10 min of uninterrupted pulsed optical excitation that was well above the corresponding lasing threshold, indicative of high photostability of the QD laser. This was in sharp contrast to organic-dye-based lasers, which underwent quick photobleaching during the laser operation under similar pumping conditions. Theoretical analysis is also carried out to elucidate the advantages of QD-based optofluidic lasers over those based on dyes. Our work opens the door to a plethora of applications where optofluidic QD lasers can replace dye-based optofluidic lasers in biosensing and on-chip miniaturized laser development.