arXiv subjects

M Krishnamurthy

Publications and source records attributed to M Krishnamurthy.

3 recordsLinked to original sources

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

A compact laser-plasma source for high-repetition-rate bi-modal X-ray and electron imaging

Bright sources of high-energy X-rays and electrons are indispensable tools in advanced imaging. Yet, current laser-driven systems typically support only single-modality imaging, require complex infrastructure, or operate at low repetition rates. Here, we demonstrate a compact, table-top laser-plasma source capable of generating synchronized electron and X-ray pulses at 1 kHz using just 2 mJ per pulse. A structured methanol droplet target enables quasi-single-shot electron radiographs and broadband, energy-resolved X-ray images, facilitating bi-modal imaging of both metallic and biological specimens. We achieve resolutions of 13.6 um for electrons and 21 um for X-rays, and demonstrate tomographic reconstruction using 35 projections. This compact platform rivals large-scale petawatt systems in resolution and brightness, while remaining scalable and accessible for high-throughput imaging in materials science and biomedicine.

physics.optics↗

arXiv2003

Electron rescattering and the fragmentation dynamics of molecules in strong optical fields

We have probed the fragmentation dynamics in a bent triatomic molecule, water, a non-planar molecule, methanol, and a planar ring-structured molecule, benzene, using 100 fs duration pulses of linearly and circularly polarized, infrared, intensity-selected laser light. At laser intensities larger than 10$^{15}$ W cm$^{-2}$, the yield of singly and multiply charged atomic fragments from these molecules is suppressed when the light is circularly polarized. At lower intensities, the fragment ion yield is not significantly polarization dependent. This hitherto-unobserved intensity dependent effect of the polarization state of light on the fragmentation dynamics is rationalized using a simple electron rescattering model. Circular polarization switches "off" electron rescattering and leads to suppression of multiple ionization and molecular fragmentation. Moreover, the degree of suppression is dependent upon the amount of energy transfer from the optical field to the molecule: the larger the energy transfer that is required for a particular fragmentation channel, the more marked is its suppression when circular polarization is used.

physics.atom-ph↗