Browsing by Subject "High Speed"

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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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    Fabrication and characterization of high speed resonant cavity enhanced Schottky photodiodes
    (1996) Islam, M. Saiful
    High speed, high external quantum efficiency and narrow spectral linewidth make resonant cavity enhanced (RC E) Schottky photodetector a good candidate for telecommunication applications. In this thesis, we present our work for the design, fabrication and characterization of a RCE Schottky photodiode with high quantum efficiency and high speed. We present experimental results on a RCE photodiode having an operating wavelength of 900 nm. The absorption takes place in a thin InGaAs layer placed inside the GaAs cavity. The active region was grown above a highreflectivity GaAs/AIAs quarter-wavelength Bragg reflector. The top mirror consisted of a 200A thin Au layer which also acted as Schottky metal of the device. An external quantum efficiency of 55% was obtained from our devices. We demonstrate that the spectral response can be tailored by etching the top surface of the microcavity. Our high speed measurements yielded a FW HM of 30 ps, which is the record response for any RCE Schottky photodiode ever reported.
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    High-speed, thermal damage-free ablation of brain tissue with femtosecond pulse bursts
    (IEEE, 2016) Kerse, Can; Yavaş, Seydi; Kalaycıoğlu, Hamit; Asik M.D.; Akçaalan, Önder; İlday, F. Ömer
    We report a novel ultrafast burst mode fiber laser system and results on ablation of rat brain tissue at rates approaching an order of magnitude improvement over previous reports, with no discernible thermal damage. © 2015 IEEE.
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    InGaAs-based high-performance p-i-n photodiodes
    (IEEE, 2002-03) Kimukin, I.; Bıyıklı, Necmi; Butun, B.; Aytur, O.; Ünlü, S. M.; Özbay, Ekmel
    In this letter, we have designed, fabricated, and characterized high-speed and high efficiency InGaAs-based p-i-n photodetectors with a resonant cavity enhanced structure. The devices were fabricated by a microwave-compatible process. By using a postprocess recess etch, we tuned the resonance wavelength from 1605 to 1558 nm while keeping the peak efficiencies above 60%. The maximum quantum efficiency was 66% at 1572 nm which was in good agreement with our theoretical calculations. The photodiode had a linear response up to 6-mW optical power, where we obtained 5-mA photocurrent at 3-V reverse bias. The photodetector had a temporal response of 16 ps at 7-V bias. After system response deconvolution, the 3-dB bandwidth of the device was 31 GHz, which corresponds to a bandwidth-efficiency product of 20 GHz.
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    Long wavelength GaAs based hot electron photoemission detectors
    (1999) Kimukin, İbrahim
    The increasing rate of telecommunication alters both science and technology, and demands high performance components. Photo detectors are essential components of optoelectronic integrated circuits and fiber optic communication systems. A new family of photodetectors offer high performance along with wavelength selectivity: resonant cavity enhanced (RCE) photodetectors. In this thesis, we present our efforts for design, fabrication and characterization of GaAs/AIGaAs based Schottky photodetectors operating within the first (850 nm) and second (1300 nm) optical communication windows. Epitaxial wafers are designed using transfer matrix method based simulation and are grown with molecular beam epitaxy. The photodetector operating at 840 nm was designed with indium tin oxide (IT O ) Schottky layer for high quantum efficiency. The second photodetector is based on internal photoemission, and is compatible with advanced GaAs process technology. Our aim with this design is high speed operation at the second optical communication window. We measured 20 GHz 3-dB bandwidth with 60% quantum efficiency at 840 nm. We expect 50 GHz 3-dB bandwidth with 0.05% quantum efficiency at 1310 nm