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Publisher: New York, NY : American Inst. of Physics × WGL Institute: MBI ×

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    Graphene Q-switched Yb:KYW planar waveguide laser
    (New York, NY : American Inst. of Physics, 2015) Kim, Jun Wan; Young Choi, Sun; Aravazhi, Shanmugam; Pollnau, Markus; Griebner, Uwe; Petrov, Valentin; Bae, Sukang; Jun Ahn, Kwang; Yeom, Dong-Il; Rotermund, Fabian
    A diode-pumped Yb:KYW planar waveguide laser, single-mode Q-switched by evanescent-field interaction with graphene, is demonstrated for the first time. Few-layer graphene grown by chemical vapor deposition is transferred onto the top of a guiding layer, which initiates stable Q-switched operation in a 2.4-cm-long waveguide laser operating near 1027 nm. Average output powers up to 34 mW and pulse durations as short as 349 ns are achieved. The measured output beam profile, clearly exhibiting a single mode, agrees well with the theoretically calculated mode intensity distribution inside the waveguide. As the pump power is increased, the repetition rate and pulse energy increase from 191 to 607 kHz and from 7.4 to 58.6 nJ, respectively, whereas the pulse duration decreases from 2.09 μs to 349 ns.
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    Photoluminescence lineshape of ZnO
    (New York, NY : American Inst. of Physics, 2014) Ullrich, B.; Singh, A.K.; Bhowmick, M.; Barik, P.; Ariza-Flores, D.; Xi, H.; Tomm, J.W.
    The merger of the absorption coefficient dispersion, retrieved from transmission by the modified Urbach rule introduced by Ullrich and Bouchenaki [Jpn. J. Appl. Phys. 30, L1285, 1991], with the extended Roosbroeck-Shockley relation reveals that the optical absorption in ZnO distinctively determines the photoluminescence lineshape. Additionally, the ab initio principles employed enable the accurate determination of the carrier lifetime without further specific probing techniques.
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    Near-field dynamics of broad area diode laser at very high pump levels
    (New York, NY : American Inst. of Physics, 2011) Hempel, M.; Tomm, J.W.; Baeumler, M.; Konstanzer, H.; Mukherjee, J.; Elsaesser, T.
    Near-field properties of the emission of broad area semiconductor diode lasers under extremely high pumping of up to ∼50 times the threshold are investigated. A transition from a gain to thermally-induced index guiding is shown under operation with single pulses of 300 ns duration. At highest output powers, catastrophic optical damage is observed which is studied in conjunction with the evolution of time-averaged filamentary near-field properties. Dynamics of the process is resolved on a picosecond time scale.