CC BY
17PLASMA SHAPING FOR RELATIVISTIC HIGH-ORDER-HARMONICS
GENERATION
S. Monchocé, S. Kahaly, A. Leblanc , Ph. Martin, F.Quéré
Lasers, Interactions and Dynamics Laboratory (LIDYL), CEA/DSM/IRAMIS, CEN Saclay, Gif sur Yvette,France
The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas [1]. The most promising of these are known as plasma mirrors (PM) [2],formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse can be used as active optical elements to manipulate its temporal and spatial properties but also to generate ultra-bright sources of isolated attosecond XUV harmonics bursts [3].
Exploiting efficiently this non-linear conversion between the incident beam wavelength and itsharmonics requires optimizing the coupling with the resulting plasma. In this talk we will demonstrate how plasma structuration of an initially solid targets can strongly improve this coupling between an ultra-high-Intensity (UHI) laser field and matter and, even more importantly, provide a unique tool for a full characterization of the harmonic spatial electric field.
The first experiments consist in applying, using a low intensity prepulse, a smooth controlled pre-plasma density. We will present a direct, quantitative experimental investigation of the influence of the interface steepness on HHG from PMs, and demonstrate the dramatic and contrasted dependences of the HHG mechanisms on this parameter [4]. In a second step, because periodic structures can couple the laser field efficiently with collective excitation plasmon modes, resulting in high laser light absorption [5], we demonstrate experimentally the feasibility of a sinusoidal plasma gratings of adjustable spatial periodicity and depth, and study the interaction of these transient structures with an ultraintense laser pulse [6].
Finally, using these gratings as a "spatial ruler", by applying the concepts of ptychography [7] to the measurements of the diffracted harmonic beam for each harmonic order in the far field, we will retrieve microscopic information on ultrahigh- intensity interactions inaccessible until now, such as the spatial amplitude and phase profiles of a laser-induced short-wavelength light source in a plasma and the structure of this plasma itself. [8].
These work, pave the way to a general approach for the emerging field of relativistic plasmonics and for the metrology of ultrahigh-intensity laser-plasma interactions on very small spatial and temporal scales.
1. Zetta-Exawatt Science and Technology, European Journal of Physics, 223, number 6 (2014)
2. B. Dromey, et al., Nature Physics 2, 456-459 (2006), C. Thaury et al., Nature Physics 3, 424 (2007)
3. J. Wheeler et al, Nat. Photonics 6, 829 (2012).
4. S. Kahaly et al, Phys. Rev. Lett. 110 175001 (2013)
5. T. Ceccoti et al, Phys.Rev. Lett, Lett. 111, 185001 (2013)
6. Monchocé et al, Phys. Rev. Lett. 112, 145008 (2014)
7. J.M. Rodenburg et al, Phys.Rev.Lett. 98, 034801 (2007)
8. A. Leblanc et al, submitted
