Sprecher
Beschreibung
The interaction between ultra-short, high-power laser pulses and solid-density targets is frequently utilized to accelerate protons [1-3] and heavier ion species [4]. Since then, it has been shown that structuring the surface leads to enhanced absorption of the laser and enhanced conversion to secondary radiation. Ruhl and Korn [5] have proposed using nanowire arrays with average density near the critical density as efficient converters from laser energy to ion energy.
Simulations predict improved laser absorption and energy conversion from laser energy to accelerated particles and radiation for shorter laser wavelengths. Furthermore, for an ideal interaction between a short laser pulse and a solid target, high temporal contrast is needed such that the solid target is still intact when interacting with the peak of the pulse. A conversion of the laser pulses via second harmonic generation (SHG) is a good way to achieve both these goals at the same time: the wavelength is shortened and the temporal contrast is improved by the highly non-linear process.
We will present recent results of laser pulses with 0.75 PW from the Ti:Sa laser system ATLAS-3000 that have been converted via SHG to high energy pulses with a wavelength of 400 nm at the Centre for Advanced Laser Applications (CALA). For the conversion, a non-linear KDP crystal (800 $\mu$m thick, 300 mm diameter, type I) has been used and a conversion efficiency of over 50$\%$ has been reached. The converted pulses contain up to 10 J of energy and the beam is focused with an f/3.2 focusing geometry, reaching intensities of $\sim 10^{21}$ W/cm$^2$ in the second harmonic. These pulses will be used for highly relativistic laser-solid interaction studies, leading the way to highly efficient laser-driven accelerators for secondary sources and novel fusion schemes.
[1] R. A. Snavely et al., Phys. Rev. Lett. 85, 2945 (2000)
[2] E. L. Clark et al., Phys. Rev. Lett. 84, 670 (2000)
[3] A. Maksimchuk et al., Phys. Rev. Lett. 84, 4108 (2000)
[4] M. Hegelich et al., Phys. Rev. Lett. 89, 085002 (2002)
[5] Ruhl and G. Korn, arXiv, 2212.1294 (2022), H. Ruhl and G. Korn, arXiv, 2302.06562 (2023)
