Controlling the Spacing of Attosecond Pulse Trains from Relativistic Surface Plasmas

Abstract

When a laser pulse hits a solid surface with relativistic intensities, XUV attosecond pulses are generated in the reflected light. We present an experimental and theoretical study of the temporal properties of attosecond pulse trains in this regime. The recorded harmonic spectra show distinct fine structures which can be explained by a varying temporal pulse spacing that can be controlled by the laser contrast. The pulse spacing is directly related to the cycle-averaged motion of the reflecting surface. Thus the harmonic spectrum contains information on the relativistic plasma dynamics.

Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

“…1(c)). The decreasing temporal spacing due to the denting of the reflection surface has also been reported by Behmke et al 31 Compared to their results, the spacing changes from one AP to the next for our few-cycle laser pulse case is so large that the spectral amplitude modulation with period <10x L is more significant than the fine structures within one harmonic order. This looks very similar to the spectra reported in the work of Borot et al 32 for similar laser pulse duration and central wavelength, but at a much lower intensity.…”

“…It also determines the denting amount of the reflecting electron surface when the peak laser intensity is fixed. 31,33 As a result, it affects the total stored electrostatic energy. In addition, it determines the release rate of electrostatic energy during the emission process when electrostatic field decays due to restoring electrons.…”

Relativistic frequency upshift to the extreme ultraviolet regime using self-induced oscillatory flying mirrors

“…In our experiments using high-contrast laser pulses, the power scaling for the harmonic spectrum agreed well with an n −8/3 dependence, and the cut-off was determined to be at the 43rd order (18.7 nm). This result, obtained with a high-contrast laser pulse, is similar to those previously reported by other groups20.…”

Beaming of High-Order Harmonics Generated from Laser-Plasma Interactions

“…The 1=e 2 radius for the ROM order shows a continuous increase until the latter stages of the laser pulse as the depth of the dent increases under the pressure of the laser. Interestingly, the effect of the dent is reduced at the end tail of the pulse where the PIC simulations show that the plasma surface ''pushes back'' towards the ion front in agreement with the study by Behmke et al [31] where this effect was studied with regard to the temporal structure of the upshifted light. Here we observe that in the higher intensity cases this effect is stronger so that the overall effect across the spot is to flatten the harmonic phase in the latter stages of the pulse.…”