Browsing by Subject "Pulses"

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    Application of a mode-locked fiber laser for highly time resolved broadband absorption spectroscopy and laser-assisted breakdown on micro-plasmas
    (IOP Publishing, 2012-05-29) Niermann, B.; Budunoglu, I. L.; Gurel, K.; Boke, M.; Ilday, F. O.; Winter, J.
    Absorption spectroscopy is known to be a powerful tool to gain spatially and temporally resolved information on excited and reactive species in a plasma discharge. Furthermore, the interaction of the discharge with short intense laser pulses can trigger the ignition and the transition into other transient states of the plasma. In this context laser-assisted 'pump-probe' experiments involving simultaneously generated supercontinuum radiation yield highly temporally resolved and spatially well-defined information on the transient phenomena. In this paper we demonstrate the possibility for 'pump-probe' experiments by initiating breakdown on a picosecond time scale ('pump') with a high-power beam and measuring the broadband absorption with the simultaneously provided supercontinuum ('probe'). Since both pulses are generated from the same mode-locked master oscillator, they have a strong level of synchronization.
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    Crystallization of Ge in SiO2 matrix by femtosecond laser processing
    (American Vacuum Society, 2012-01-19) Salihoglu, O.; Kürüm, U.; Yaglioglu, H. G.; Elmali, A.; Aydınlı, Atilla
    Germanium nanocrystals embedded in a siliconoxide matrix has been fabricated by single femtosecond laser pulse irradiation of germanium doped SiO2 thin films deposited with plasma enhanced chemical vapor deposition. SEM and AFM are used to analyze surface modification induced by laser irradiation. Crystallization of Ge in the oxide matrix is monitored with the optic phonon at 300 cm(-1) as a function of laser fluence. Both the position the linewidth of the phonon provides clear signature for crystallization of Ge. In PL experiments, strong luminescence around 600 nm has been observed.
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    ItemOpen Access
    Diffraction-limited, 10-W, 5-ns, 100-kHz, all fiber laser at 1.55 um
    (Optical Society of America, 2014-04-25) Pavlov, I.; Dulgergil, E.; Ilbey, E.; Ilday, F. O.
    This Letter reports on an all-fiber-integrated master-oscillator, power amplifier system at 1.55 mu m producing 5-ns, 100-mu J pulses. These pulses are generated at a 100 kHz repetition rate, corresponding to 10 W of average power. The seed source is a low-power, current-modulated, single-frequency, distributed feedback semiconductor laser. System output is obtained from a standard single-mode fiber (Corning SMF-28). Consequently, the beam is truly diffraction limited, which was independently proven by M-2 measurements. Further increase of peak power is limited by onset of significant spectral broadening due to nonlinear effects, primarily four-wave mixing. Numerical simulations based on six-level rate equations with full position-and time-dependence were developed to model propagation of pulses through the amplifier chain. This capability allows minimization of the amplified spontaneous emission, which can be directly measured using a fast acousto-optic modulator to gate the pulses. (C) 2014 Optical Society of America