22 W average power multiterawatt femtosecond laser chain enabling 1019 W/cm2 at 100 Hz

Abstract

We measure the wavefront distortions of a high peak power ultrashort (23 fs) laser system under high average power load. After 6 min-100 Hz operation of the laser at full average power (> 22 W after compression), the thermally induced wavefront distortions reach a steady state and the far-field profile of the laser beam no longer changes. By means of a deformable mirror located after the vacuum compressor, we apply a static pre-compensation to correct those aberrations allowing us to demonstrate a dramatic improvement of the far-field profile at 100 Hz with the reduction of the residual wavefront distortions below λ/16 before focusing. The applied technique provides 100 Hz operation of the femtosecond laser chain with stable pulse characteristics, corresponding to peak intensity above 10 19 W/cm 2 and average power of 19 W on target, which enables the study of relativistic optics at high repetition rate using a moderate f-number focusing optics (f/4.5).

Exploring phase contrast imaging with a laser-based Kα x-ray source up to relativistic laser intensity

“…To evaluate the interest of K α x-ray sources generated with ultrahigh laser intensity for fast PCI applications, we perform the experiments with the 100 Hz, 10-TW, 800 nm laser beamline 42 of ASUR facility, a unique laser combining high average and high peak power. The p-polarized laser beam of ~25 fs pulse duration is focused on a molybdenum (Mo, α E K = 17.48 keV) thick target at an angle of incidence of 45° with an off-axis parabola (Fig.…”

High photon flux Kα Mo x-ray source driven by a multi-terawatt femtosecond laser at 100 Hz

“…We also evaluated the importance of wavefront aberrations induced by the laser average power developing in the compressor and in beam transport optics related to the operation of the 100 Hz-multi-terawatt laser driving source. We observe that, even at high average power (>10 W), the thermally induced wavefront aberrations have no time to develop for a reduced number of shots (typically ∼1000 shots − 10 s) [14]. In this Letter, in order to evaluate the performance of our x-ray source as a function of the driving intensity, we thus limit the number of shots to 1000 when the average power exceeds 10 W. To generate the x-ray source, the laser beam is focused at an angle of incidence of 45°by an off-axis parabolic (OAP) mirror (effective focal length 150 mm) on a rotating thick molybdenum (Mo) disk (6 mm thickness and 100 mm in diameter) with a polished surface (roughness < 1 μm).…”

“…The K α x-ray source is generated using a p-polarized beamline (nominal performances: 800 nm, 220 mJ, 25 fs, 100 Hz, ns temporal contrast ratio (CR) I peak,fs ∕I background,ns 10 10 ) of LP3-ASUR facility [14]. Experimental details of the driving laser source, beam transport to the Mo target, and x-ray source diagnostics can be found in Refs.…”

“…Experimental details of the driving laser source, beam transport to the Mo target, and x-ray source diagnostics can be found in Refs. [7,14]. We recall hereafter only specific points related to running such experiments at 100 Hz.…”

“…Further studies to improve the x-ray source efficiency will be to use thin foils and microstructured targets. Ultimately, in view of running a powerful 100 Hz laserbased x-ray source largely over minutes (≫ 1000 shots), we dispose of an available strategy [14] to pre-compensate for the reduction of the wavefront quality of the 100 Hz laser system. a The table presents laser parameters for each reported work: energy, intensity, temporal CR, and repetition rate.…”