High repetition rate (100Hz), high peak intensity (1019W.cm−2), high contrast femtosecond laser chain

Summary form only given. High intensity femtosecond lasers are now routinely used to produce energetic particles and photons via interaction with solid targets [1-2]. However, the relatively low conversion efficiency of such processes requires the use of high repetition rate laser to increase the average power of the laser-induced secondary sources [3]. Furthermore, for high intensity laser-matter interaction, a high temporal contrast is of primary importance as the presence of an ASE pedestal (Amplified Spontaneous Emission) and/or various prepulses may significantly affect the laser-matter interaction processes by creating a pre-plasma on the target surface. We present the characterization of a laser chain based on Ti:Sa technology and CPA technique, which presents unique laser characteristics: a high repetition rate (100 Hz), a high peak power (> 7 TW on target), a good energy stability (see Figure 1a) and a high contrast ratio (ASE <; 10-10, see Figure 1b) obtained thanks to a specific design with 3 saturable absorbers inserted in the amplification chain [4]. We demonstrated that the laser beam distortions induced by the high thermal load (>30 W) incoming on the compressor grating could be mostly compensated by our adaptive optic system. We also studied the impact of these thermally induced distortions in the temporal profile of the recompressed pulse (see Figure 1c). In these conditions, we achieved peak intensities above 1019W.cm-2 on target at 100 Hz, allowing the study of relativistic optics at a high repetition rate. We indeed demonstrated the generation of KD X-ray sources at 100 Hz with characteristics (efficiency > 10-5 at I = 5. 1018 W/cm2) close to our former results obtained with a high contrast multi-TW source at 10 Hz.