Berlin 2014 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 30: Poster: Photonics, laser development and applications, ultrashort laser pulses, quantum effects

Q 30.58: Poster

Dienstag, 18. März 2014, 16:30–18:30, Spree-Palais

Changing the spatial beam profile of shaped femtosecond pulses on an ultrafast time scale — •Tom Bolze and Patrick Nuernberger — Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg

Femtosecond pulse shaping is routinely employed to selectively change the amplitude, the spectral phase, and the polarisation state of the laser pulses. However, only a few studies have adressed the aspect of modifying the spatial beam profile within a single laser pulse.

We present a concept to shape the spatial intensity distribution of a femtosecond laser pulse on the ultrafast timescale. To this end, the laser beam is sent through a Mach-Zehnder-type interferometer. In one arm, a spiral phase plate generates a pulse with a Laguerre-Gaussian (LG) spatial beam profile, and additionally a glass rod imprints a large positive chirp. The laser pulse in the other interferometer arm receives the same amount of chirp, but with opposite sign, by a femtosecond pulse shaper. However, its spatial intensity distribution remains the fundamental Hermite-Gaussian (HG) mode. After the interferometer, the LG pulse and the HG pulse are recombined and interfere. This leads to a corkscrew-like motion of the spatial intensity distribution, spiraling around the beam axis on the time scale of the pulse's duration.