High-contrast 10-fs OPCPA-based Front-End for the Apollon-10PW laser (Orale)

International audienceWe present a high-contrast 10-fs Front-End for Ti:sapphire PW-lasers within the Apollon-10PW project. This injector uses OPCPA pumped at 100 Hz by Yb-based CPA chain. Combination of OPCPA and XPW permits a >10 12 contrast ratio

Génération d'impulsions laser ultra brèves et ultra intenses à contraste temporel élevé

PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF

Spectral coherence properties of continuum generation in bulk crystals

The stability of the phase difference between two white-light continua, generated from the same 180-fs pulses at 1035\,nm, is assessed by a modified Bellini-Hansch interferometer. Mutual spectral stability is studied as a function of several parameters: position of the nonlinear crystal with respect to the beam waist, interaction length, and pulse energy. Intensity-to-phase coupling coefficients are measured and stability regions are identified

Femtosecond laser-induced damage threshold of electron beam deposited dielectrics for 1-m class optics

International audienc

Off-axis aberration compensation of focusing with spherical mirrors using deformable mirrors

International audienceWe studied the possibility of focusing an ultra-intense laser beam with a spherical mirror instead of a parabolic mirror. To correct the induced wavefront aberrations, we used a deformable mirror in a closed-loop configuration with a Shack–Hartmann Wavefront Sensor (SHWS). We demonstrate in this paper that we were able to correct the aberrations induced by spherical mirrors down to an f-number equal to 3.3

Experimental evidence of 25-fs laser pulse distortion in singlet beam expanders

International audienceWe report the measurement of spatiotemporal distortions of an ultrashort pulse in singlet beam expanders. With a simple second-order autocorrelator the temporal broadening of the pulse from 23 to 40 fs, due to propagation time difference (PTD), is determined. The delay due to PTD between different parts of the beam is also measured. This effect was theoretically studied for the first time by Bor [J. Mod. Opt. 35, 1907 (1988)]. These experimental results are in good agreement with the calculations of a dedicated three-dimensional ray-tracing program developed to simulate the spatial and temporal transformation of femtosecond pulses in optical systems

14-fs high temporal quality injector for ultra-high intensity laser

International audienceWe present a chirped pulse amplification (CPA) Ti:Sa laser generating sub-15 fs pulses with expected high temporal quality. Gain-narrowing in the pre-amplifier is balanced by a variable spectral reflectivity mirror and by a fine adaptation of the saturation conditions. A crossed polarized wave generation (XPW) filter is introduced to enhance the contrast, reduce the pulse duration and improve the spectral quality. The pulses are generated at 10 Hz repetition rate, with pulse energy of 110 μJ and very clean Gaussian spectrum. The temporal contrast is evaluated by a measurement before the XPW filter and calculations of the enhancement by the filter. The potential temporal incoherent contrast is 10^12 and the coherent contrast 10^10. The performances of the system make it suitable as an injector for petawatt lasers operating in the double CPA scheme

Adaptive wavefront correction on a 100-TW/10-Hz chirped pulse amplification laser and effect of residual wavefront on beam propagation

International audienceWe demonstrate the wavefront correction of a 100-TW (25 fs, 2.5 J) high repetition rate Ti:sapphire laser. A 36-actuator bimorph deformable mirror was used under vacuum and the adaptive optic system is working at 10 Hz in a closed-loop configuration with a Shack–Hartmann wavefront sensor. We also numerically studied the effects of the deformable mirror actuators on laser beam free propagation to determine the ideal position of the deformable mirror in the laser chain. Our ability to focus the beam was improved to near-diffraction-limited quality and intensity as high as 1.4 × 10^20 W/cm^2 was reached with a 500-mm focal length off-axis parabolic mirror

Highly efficient temporal cleaner for femtosecond pulses based on cross-polarized wave generation in a dual crystal scheme

International audienceWe present an experimental demonstration of a renewed set up, with respect to the one described in [A. Jullien et al, Opt. Lett. 30, 920 (2005)], that enables more reliable and robust performances in the increase of the contrast ratio (CR) of energetic femtosecond pulses. The new approach is based on the use of two successive crystals situated at optimum position that generate cross polarized waves whose individual effect interferes constructively. This arrangement overcomes the limitation of the single crystal schemes for temporal cleaning – the early saturation of the transmission efficiency, previously observed when either using a relatively thick crystal or increasing intensities up to its damage threshold. A theoretical model that predicts the output CR is developed for the first time. It shows that the CR depends on the initial CR and the extinction ratio of the polarizers used. The measured temporal CR 10^-10 is in accordance with theoretical predictions

Amplification of Femtosecond Laser Filaments in Ti:Sapphire

International audienceFemtosecond laser filamentation is studied in a broadband amplifying medium, sapphire doped with electronically excited Ti ions. Evidence for fluence amplification of self-guided pulses, increase of filamentation length, as well as a lowering of the input laser power necessary for filamentation is reported