arXiv subjects

Sk Rakeeb

Publications and source records attributed to Sk Rakeeb.

8 recordsLinked to original sources

arXiv2026

Quasi-static transverse electric field driven electron acceleration in relativistic laser matter interaction

Achieving significant energy gain in laser-driven relativistic electron beams remains challenging due to dephasing between the accelerating laser field and the electrons. We show that transverse electric fields, when aligned with the plane of laser polarization, can mitigate dephasing and enable substantial energy gain without compromising beam directionality. As a practical realization, we propose a two-laser scheme in which one laser generates the transverse field while the other drives electron acceleration. By tailoring the interaction geometry, this configuration sustains phase locking, enhances energy transfer, and opens a pathway toward compact, high-efficiency electron accelerators.

physics.plasm-ph↗

arXiv2026

Tens of MeV, collimated, bright fluxes of protons from ordered nano-structured targets in ultra-relativistic laser-matter interaction

Laser-driven proton acceleration from nanostructured solid targets has been extensively studied, yet its performance under realistic temporal contrast conditions at petawatt-class facilities remains an open question. We present an experimental investigation of proton generation from nanostructured and flat solid targets performed at the ELI-NP facility using femtosecond laser pulses at peak intensities of $\sim 3\times10^{21}$ \wcm. Proton spectra are compared for two contrast regimes: $\sim 10^{-10}$ without plasma mirror and $\sim 10^{-13}$ with single plasma mirror. Importantly, measurable enhancement in the cutoff energy persists for the nanowire targets at both contrast levels, indicating robustness of nanowire targets against moderate pre-pulse intensities. Alongside, study of energy resolved angular distribution reveals that nanowires promote more directional emission with higher flux of high-energy protons along the target normal, while flat targets produce broader angular distributions. The results are well supported and explained by 3D particle-in-cell simulations.

physics.plasm-ph↗

arXiv2026

Bright, directional electron emission from nanowire coated targets under petawatt, femtosecond irradiation

Interactions of relativistically intense laser pulses with structured targets have long been explored for controlling energy absorption and particle acceleration. However, at upcoming multi-petawatt laser facilities, the survivability of such nanostructures under realistic temporal contrast conditions remains a key concern. We report an experimental and simulation study of nanowire targets irradiated by the ELI-NP 1-PW laser without a plasma mirror. At the built in, readily available contrast of $10^{-10}$, the nanowires survive the laser pre-pulse and produce a robust enhancement in relativistic electron flux, energy, and directional emission compared to flat targets indicating that at better contrasts they can show similar enhancement at the 10 PW level. These results establish nanowire targets as resilient and reliable tools for relativistic electron manipulation at state of the art facilities.

physics.plasm-ph↗

arXiv2025

Impulsive excitation of a solid by extreme contrast, high intensity femtosecond laser pulses

We present the ultra-fast dynamics of the interaction between a high-intensity extreme contrast (expected to be around 1e-18 at hundreds of picoseconds timescale) femtosecond laser and a solid. Simultaneous measurements of probe Doppler spectrometry and reflectivity in pump-probe experiments reveal the presence of extreme pressure in the solid density region, which triggers a long-lived (about 15 ps) strong inward shock. Hydrodynamic simulations accurately replicate these observations, providing a detailed explanation of the underlying physics

physics.plasm-ph↗

arXiv2025

Spatial, Spectral and Temporal Response of High Intensity Laser Plasma Mirrors- Direct Observation of the Ponderomotive Push

Plasma-based optics have emerged as a powerful platform for manipulating and amplifying ultra-intense laser pulses. However, the inherently nonlinear and dynamic nature of plasma leads to significant spatial, spectral, and temporal modulations when driven at relativistic intensities. These modifications can dramatically alter the structure of the reflected laser pulses, posing challenges for their use in applications such as vacuum ultraviolet (VUV) and X-ray generation, as well as relativistic particle acceleration. Comprehensive, multidimensional diagnostics are essential to accurately characterize these so-called `plasma mirrors' (PMs). We present a direct, \textit{in situ} measurement of the three-dimensional plasma surface evolution during femtosecond laser irradiation, achieved through simultaneous analysis of the wavefront, spectrum, and temporal profile of the reflected light. Our measurements reveal surface deformations on the order of a few hundred nanometers at relativistic intensities, in agreement with three-dimensional particle-in-cell (3D-PIC) simulations. Additionally, the PM induces substantial modifications to the pulse spectrum and temporal profile, introducing spatio-temporal couplings.

physics.plasm-ph↗

arXiv2025

Capturing the three dimensional, nano-scale, pico-second dynamics of plasma mirrors with intense ultrashort laser wavefront measurement

We present a direct measurement of the nanoscale dynamics of plasma mirrors using wavefront measurement techniques. This two-dimensional measurement, performed via pump-probe diagnostics, enables the reconstruction of the three-dimensional plasma mirror surface with nanometer axial, micrometer transverse, and femtosecond temporal resolution.

physics.plasm-ph↗

arXiv2024

Femtosecond dynamics on the nanoscale of intense laser-induced grating plasma

The complex interaction dynamics of intense femtosecond (fs) pulses and their picosecond (ps)-long leading edge with nanostructured solids occur at both the nanometer and the femtosecond scales, making them extremely difficult to measure directly. Here, we present pump-probe-based measurements that capture the ultrafast evolution of relativistically intense laser-driven grating plasma on fs time and nanometer spatial scales. We measure the transient reflectivity and spectrum of the scattered or diffracted UV-probe pulses from the grating structures with 100s of fs resolution. Our measurements capture the initial onset of the solid-to-plasma transition and the subsequent grating plasma expansion, a few ps before the peak of the intense fs pulse. We measure the instantaneous position of the electron critical surface, its velocity, and its acceleration, which are very crucial for fundamental understanding and applications in ion/electron acceleration and high harmonic generation, while also providing valuable benchmarks for simulations. Particle-in-cell (PIC) simulations corroborate the observations well offering further insight into this process.

physics.plasm-ph↗

arXiv2024

Coherent Control of Relativistic Electron Dynamics in Plasma Nanophotonics

Intense femtosecond laser pulses interacting with solids can drive electrons to relativistic energies, enabling miniaturized particle accelerators and bright extreme-ultraviolet light sources. In-situ space-time control of these electrons is crucial for developing next-generation laser-based accelerators but remains extremely challenging. We present a novel approach to achieve such control by manipulating the local fields driving these electrons using a nanoengineered dielectric nanopillar target. We demonstrate via experiments and simulations that this sub-femtosecond and nanometer-scale control enables enhanced electron acceleration and control of the directionality of relativistic electrons over a wide angular range and predicts the coherent formation of sub-femtosecond electron bunches from the nanopillars. This research bridges nanophotonics and strong-field plasma physics, offering new opportunities for in-situ control of high-energy particles and advancements in plasma technology.

physics.plasm-ph↗