Hollow Plasma Acceleration Driven by a Relativistic Reflected Hollow Laser

In order to address the present difficulty in experimentally generating the relativistic Laguerre-Gaussian laser, primarily due to damage caused to optical modulators, a high-reflectivity phase mirror is applied in the femtosecond petawatt laser system to generate a relativistic hollow laser at the highest intensity of $6.3\times {10}^{19}\mathrm{W}/{\mathrm{cm}}^2$ for the first time. A simple optical model is used to verify that the vortex laser may be generated in this new scheme; using such a relativistic vortex laser, the hollow plasma drill and acceleration are achieved experimentally and proven by particle-in-cell simulations. With the development of the petawatt laser, this scheme opens up possibilities for the convenient production of the relativistic hollow laser at high repetition and possible hollow plasma acceleration, which is important for a wide range of applications such as the generation of radiation sources with orbital angular momentum, fast ignition for inertial confinement fusion, and jet research in the astrophysical environment.

Figure 1

(a) Experimental setup. Intensity distributions of the (b) LG and (c) Gaussian laser at focus. (d) Structure of the phase plate.

Figure 2

Laser intensity distributions in (a) $x-z$ plane, $x-y$ planes at (b) $z=-500$ and (c) $z=0\mu \mathrm{m}$. Distributions of electric field (d) $Ex$ and (e) $Ey$ at focus ($z=0\mu \mathrm{m}$); (f) and (g) are the corresponding phase distributions of (d) and (e).

Figure 3

Proton imaging on RCFs driven by (a)–(c) a Gaussian laser with 9 J, a LG laser with (d)–(f) 13, (g)–(i) 9, and (k)-(m) 7 J, respectively. Spatial distribution of protons on RCF in experiments (dash line) and simulations (solid line) for the case of (n) Fig. 3 and (o) Fig. 3. Here, the angular axis is the target normal direction determined by the laser focal spot and the hole on the RCF. (p) Images on the IP plate. (q) Energetic spectra in the case of a Gaussian laser with 9 J (black square), and a LG laser with 13 (red square), 9 (blue triangle), and 7 J (wine diamond) in experiments.

Figure 4

(a) Profile of the laser in experiments. (b) Density distribution driven by the prepulse in a 1D MULTI simulation. The corresponding density of proton $n_p$ (black), ${\mathrm{C}}^{4+}$ ions $n_C$ (red), and electrons $n_e$ (blue) is designed in the inset plot for the PIC simulations.

Figure 5

Distributions of (a)–(c) electric field $Ez$, (d)–(f) electron density, (g)–(i) proton density at 60 (first row), 80 (second row), and 200 T (third row). (j) Proton spectra driven by a Gaussian laser with 9 J (solid line), a LG laser with 13 (dashed line), 9 (dotted line), and 7 J (dashed-dotted line) at $t=200\mathrm{T}$. (k) Evolution of electron temperature (red square) and Mach number $M$ (black circle). Energetic envelope of the proton layer driven by (l) a LG laser and (m) a Gaussian laser $t=200\mathrm{T}$. (n) Angular distributions for LG (black solid line) and Gaussian laser (red dashed line).