Sprecher
Beschreibung
Most characteristics of ultra-short laser pulses can be obtained by measuring the integrated spectrum or only slices in space. However, Spatio-Temporal Couplings (STCs) may influence the laser performance. Common measurement techniques usually either rely on scanning over hundreds of shots, are only sensitive to low order effects like the Pulse-Front Tilt (PFT) or have the trade-off of significantly reduced spatial and spectral resolution.
With the introduction of FALCON [1] we already presented a simple device that is based on narrow bandpass filters in front of a Shack-Hartmann (SH) sensor. With the robust modal Zernike-Taylor coefficient reconstruction it allows to reconstruct STCs in only a few shots. With Single Shot FALCON, we present a complementary follow up, that can be used in the same setup (Fig.1), and consists of nine bandpass filters stacked in a mosaic like manner. This allows for single-shot reconstructions although there is only incomplete spatial data for each filter, due to the modal reconstruction working also on sub apertures of the beam.
We overcome the disadvantage of having less data points for each reconstruction by implementing a Bayesian inference scheme to include prior knowledge that we acquire from prior FALCON or Single Shot FALCON measurements. We use the information of the prior mean and uncertainty to influence the result of each single shot measurement. For a steady state laser system, this allows to gain more confidence on the results for subsequent single shot measurements. For a moving system, this prior knowledge sets the parameter space at which STC coefficients may change as typically laser pulses do not drastically vary in all parameters at the same time. For the case of drastic changes in single parameters or accumulated strong drifts we included competing Bayesian models with different uncertainties, where we evaluate which model describes the current system best for each shot via the Bayes factor.
We show the functionality of this monitoring scheme for experiments with the ATLAS-3000 Laser at the Centre for Advanced Laser Applications in Garching.
