Browsing by Author "Yavaş, S."

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    Ablation-cooled material removal at high speed with femtosecond pulse bursts
    (OSA, 2015) Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Akçaalan, Önder; Yavaş, S.; Aşık, M. D.; Kesim, Deniz Koray; Yavuz, Koray; Çetin, Barbaros; İlday, Fatih Ömer
    We report exploitation of ablation cooling, a concept well-known in rocket design, to remove materials, including metals, silicon, hard and soft tissue. Exciting possibilities include ablation using sub-microjoule pulses with efficiencies of 100-mJ pulses.
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    Nonlinear laser lithography for indefinitely large-area nanostructuring with femtosecond pulses
    (Nature publishing group, 2013) Öktem, B.; Pavlov, I.; Ilday, S.; Kalaycıoǧlu, H.; Rybak, A.; Yavaş, S.; Erdoǧan, M.; Ilday F. Ö.
    Dynamical systems based on the interplay of nonlinear feedback mechanisms are ubiquitous in nature. Well-understood examples from photonics include mode locking and a broad class of fractal optics, including self-similarity. In addition to the fundamental interest in such systems, fascinating technical functionalities that are difficult or even impossible to achieve with linear systems can emerge naturally from them if the right control tools can be applied. Here, we demonstrate a method that exploits positive nonlocal feedback to initiate, and negative local feedback to regulate, the growth of ultrafast laser-induced metal-oxide nanostructures with unprecedented uniformity, at high speed, low cost and on non-planar or flexible surfaces. The nonlocal nature of the feedback allows us to stitch the nanostructures seamlessly, enabling coverage of indefinitely large areas with subnanometre uniformity in periodicity. We demonstrate our approach through the fabrication of titanium dioxide and tungsten oxide nanostructures, but it can also be extended to a large variety of other materials.
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    Optical resolution photoacoustic imaging of multiple probes via single fiber laser with independently adjustable parameters
    (OSA, 2017) Yavaş, S.; Kipergil, E. A.; Uluç, N.; Demirkıran, A.; Kayıkçıoğlu, T.; Salman, H. S.; Karamuk, Şöhret Görkem; Ünlü, M. B.; İlday, Fatih Ömer
    Photoacoustic microscopy (PAM) is a promising imaging modality that combines optical and ultrasound imaging. It combines the advantages of high ultrasonic spatial resolution and high optical contrast. When a short laser pulse illuminates the tissue, absorbed light leads to an acoustic emission via thermoelastic expansion. The laser system needs to generate short enough pulses, i.e., several nanoseconds, to create photoacoustic signals with high efficiency and emit wavelengths in the visible range to excite tissue chromophores in their absorption peaks. To increase penetration depth of imaging, it is also desirable to utilize a wavelength in the NIR range, from 600 to 1200 nm, where biological tissues are relatively transparent.
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    Response of porcine articular cartilage to irradiation by an ultrafast, burst-mode laser
    (Optical Society of America (OSA), 2019) Dzelzainis, T.; Hammouti, S.; Prickaerts, M.; Cassidy, K.; İlday, F. Ömer; Kalaycıoğlu, Hamit; Yavaş, S.; Karamuk, Ş.; Golaraei, A.; Barzda, V.; Akens, M.; Lilge, L.; Marjoribanks, R.
    Plasma-mediated ablation by ultrafast pulses is generally considered to be a material-independent process. We show that, in certain circumstances, this assumption may be invalid. Physical processes involved and the impact on applications are discussed.
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    Surface texturing of dental implant surfaces with an ultrafast fiber laser
    (Optical Society of America, 2010) Öktem, Bülent; Kalaycıoğlu, Hamit; Erdoǧan, M.; Yavaş, S.; Mukhopadhyay P.; Tazebay, Uygar Halis; Aykaç, Y.; Eken, K.; İlday, F. Ömer
    Controlled modification of implant surfaces using femtosecond, picosecond and nanosecond pulses from home-built all-fiber-integrated lasers is demonstrated. Picosecond and femtosecond pulses offer superior control over the surface texture. Increasing cell attachment to surface is discussed. ©2010 Optical Society of America.
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    Texturing of titanium (Ti6Al4V) medical implant surfaces with MHz-repetition-rate femtosecond and picosecond Yb-doped fiber lasers
    (Optical Society of American (OSA), 2011) Erdoǧan, M.; Öktem, B.; Kalaycioǧlu H.; Yavaş, S.; Mukhopadhyay P.K.; Eken, K.; Özgören, K.; Aykaç, Y.; Tazebay, U.H.; Ilday F.O.
    We propose and demonstrate the use of short pulsed fiber lasers in surface texturing using MHz-repetition-rate, microjoule- and sub-microjoule-energy pulses. Texturing of titanium-based (Ti6Al4V) dental implant surfaces is achieved using femtosecond, picosecond and (for comparison) nanosecond pulses with the aim of controlling attachment of human cells onto the surface. Femtosecond and picosecond pulses yield similar results in the creation of micron-scale textures with greatly reduced or no thermal heat effects, whereas nanosecond pulses result in strong thermal effects. Various surface textures are created with excellent uniformity and repeatability on a desired portion of the surface. The effects of the surface texturing on the attachment and proliferation of cells are characterized under cell culture conditions. Our data indicate that picosecond-pulsed laser modification can be utilized effectively in low-cost laser surface engineering of medical implants, where different areas on the surface can be made cell-attachment friendly or hostile through the use of different patterns. © 2011 Optical Society of America.