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Start date: 2014 × Subject: Beam parameter ×

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    Experimental strategies for optical pump - Soft x-ray probe experiments at the LCLS
    (Bristol : Institute of Physics Publishing, 2014) McFarland, B.K.; Berrah, N.; Bostedt, C.; Bozek, J.; Bucksbaum, P.H.; Castagna, J.C.; Coffee, R.N.; Cryan, J.P.; Fang, L.; Farrell, J.P.; Feifel, R.; Gaffney, K.J.; Glownia, J.M.; Martinez, T.J.; Miyabe, S.; Mucke, M.; Murphy, B.; Natan, A.; Osipov, T.; Petrovic, V.S.; Schorb, S.; Schultz, T.; Spector, L.S.; Swiggers, M.; Tarantelli, F.; Tenney, I.; Wang, S.; White, J.L.; White, W.; Gühr, M.
    Free electron laser (FEL) based x-ray sources show great promise for use in ultrafast molecular studies due to the short pulse durations and site/element sensitivity in this spectral range. However, the self amplified spontaneous emission (SASE) process mostly used in FELs is intrinsically noisy resulting in highly fluctuating beam parameters. Additionally timing synchronization of optical and FEL sources adds delay jitter in pump-probe experiments. We show how we mitigate the effects of source noise for the case of ultrafast molecular spectroscopy of the nucleobase thymine. Using binning and resorting techniques allows us to increase time and spectral resolution. In addition, choosing observables independent of noisy beam parameters enhances the signal fidelity.
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    783 nm wavelength stabilized DBR tapered diode lasers with a 7 W output power
    (Washington, DC : The Optical Society, 2021) Sumpf, Bernd; Theurer, Lara Sophie; Maiwald, Martin; Müller, André; Maaßdorf, André; Fricke, Jörg; Ressel, Peter; Tränkle, Günther
    Wavelength stabilized distributed Bragg reflector (DBR) tapered diode lasers at 783 nm will be presented. The devices are based on GaAsP single quantum wells embedded in a large optical cavity leading to a vertical far field angle of about 29◦ (full width at half maximum). The 3-inch (7.62 cm) wafers are grown using metalorganic vapor phase epitaxy. In a full wafer process, 4 mm long DBR tapered lasers are manufactured. The devices consist of a 500 µm long 10th order surface DBR grating that acts as rear side mirror. After that, a 1 mm long ridge waveguide section is realized for lateral confinement, which is connected to a 2.5 mm long flared section having a full taper angle of 6◦. At an injection current of 8 A, a maximum output power of about 7 W is measured. At output powers up to 6 W, the measured emission width limited by the resolution of the spectrometer is smaller than 19 pm. Measured at 1/e2 level at this output power, the lateral beam waist width is 11.5 µm, the lateral far field angle 12.5◦, and the lateral beam parameter M2 2.5. The respective parameters measured using the second moments are 31 µm, 15.2◦, and 8.3. 70% of the emitted power is originated from the central lobe. © 2021 Optical Society of America