Characterisation, wavefront reconstruction and propagation of ultra-broadband laser pulses from Hartmann-Shack measurements

The wave-front of a beam effects both, irradiance and phase distribution near focus, and thus yields large impact on the efficiency of non-linear coherent processes as generation of higher harmonics from fs laser pulses. Here we present Hartmann-Shack wave-front measurements of ultra-broadband pulses, which are produced by focussing pulses from a Ti-Sa oscillator-amplifier system into an Argon filled hollow fiber. After re-compression the pulses were analyzed behind the fiber exit, as well as after reflection from a concave mirror. Measurements of the overall polychromatic wave-front are faced to quasi-monochromatic ones, covering the spectrum. Incoherent superposition of the spectral components yields excellent agreement to the measured overall wave-front showing, that the total wave-front can be sensed reliably by a single wave-front measurement. Furthermore, comparison of numerically propagated and measured wave-fronts shows good agreement for different spectral components, and the measured overall wave-front fits, within sensor accuracy, the average one propagated. Drawbacks and opportunities of the Hartmann-Shack technique in ultra-short pulse sensing are briefly discussed.