Aligned copper nanorod arrays for highly efficient generation of intense ultra-broadband THz pulses

Near-critical plasmas irradiated at ultra-high laser intensities (I > 1018W/cm2) allow to improve the performances of laser-driven particle and radiation sources and to explore scenarios of great astrophysical interest. Near-critical plasmas with controlled properties can be obtained with nanostructured low-density materials. By means of 3D Particle-In-Cell simulations, we investigate how realistic nanostructures influence the interaction of an ultra-intense laser with a plasma having a near-critical average electron density. We find that the presence of a nanostructure strongly reduces the effect of pulse polarization and enhances the energy absorbed by the ion population, while generally leading to a significant decrease of the electron temperature with respect to a homogeneous near-critical plasma. We also observe an effect of the nanostructure morphology. These results are relevant both for a fundamental understanding and for the foreseen applications of laser-plasma interaction in the near-critical regime.

Section: Introductionmentioning

confidence: 99%

Ultra-intense laser interaction with nanostructured near-critical plasmas

Fedeli

Formenti

Cialfi

et al. 2018

“…More recently, arrays of Si micro-wires irradiated by ultra-short joule-class laser pulses ( I ~ 1 × 10 21 W/cm 2 ) have generated electron beams with increased total and cut-off energies, from 30 to 70 MeV 23 . Furthermore, it has also been demonstrated that aligned Cu-nanorod arrays irradiated by sub-joule ultra-short laser pulses ( I ~ 3.5 × 10 18 W/cm 2 ) can generate intense broadband terahertz sources 24 .…”

Section: Introductionmentioning

confidence: 99%

Enhancing laser-driven proton acceleration by using micro-pillar arrays at high drive energy

Khaghani

Lobet

Borm

et al. 2017

The interaction of micro-and nano-structured target surfaces with high-power laser pulses is being widely investigated for its unprecedented absorption efficiency. We have developed vertically aligned metallic micro-pillar arrays for laser-driven proton acceleration experiments. We demonstrate that such targets help strengthen interaction mechanisms when irradiated with high-energy-class laser pulses of intensities ~10 17-18 W/cm 2 . In comparison with standard planar targets, we witness strongly enhanced hot-electron production and proton acceleration both in terms of maximum energies and particle numbers. Supporting our experimental results, two-dimensional particle-in-cell simulations show an increase in laser energy conversion into hot electrons, leading to stronger acceleration fields. This opens a window of opportunity for further improvements of laser-driven ion acceleration systems.Laser-driven proton beams have attracted increasing interest due to their unique properties and many applications 1, 2

“…First theoretical and numerical estimations made by Wang et al 43 have shown that this target type allows for an enhanced laser energy absorption. The same nanowire geometry has been demonstrated experimentally to be very effective for enhanced THz pulse generation 44 , and several other works have demonstrated enhanced X-ray emission though greater electron heating with nano-velvets 45 and nanowires 46 – 48 . The high aspect ratio between length and diameter of NWs favors an increased laser absorption due to a greater effective interaction surface area with the incoming electromagnetic (EM) wave, occurring within a few laser cycles such as to maximize the interaction with the intact NW forest.…”

Section: Introductionmentioning

confidence: 86%

Enhanced laser-driven proton acceleration using nanowire targets

Vallières

Salvadori

Permogorov

et al. 2021

Self Cite

Laser-driven proton acceleration is a growing field of interest in the high-power laser community. One of the big challenges related to the most routinely used laser-driven ion acceleration mechanism, Target-Normal Sheath Acceleration (TNSA), is to enhance the laser-to-proton energy transfer such as to maximize the proton kinetic energy and number. A way to achieve this is using nanostructured target surfaces in the laser-matter interaction. In this paper, we show that nanowire structures can increase the maximum proton energy by a factor of two, triple the proton temperature and boost the proton numbers, in a campaign performed on the ultra-high contrast 10 TW laser at the Lund Laser Center (LLC). The optimal nanowire length, generating maximum proton energies around 6 MeV, is around 1–2 $$\upmu$$ μ m. This nanowire length is sufficient to form well-defined highly-absorptive NW forests and short enough to minimize the energy loss of hot electrons going through the target bulk. Results are further supported by Particle-In-Cell simulations. Systematically analyzing nanowire length, diameter and gap size, we examine the underlying physical mechanisms that are provoking the enhancement of the longitudinal accelerating electric field. The parameter scan analysis shows that optimizing the spatial gap between the nanowires leads to larger enhancement than by the nanowire diameter and length, through increased electron heating.