Dependence of fast electron characteristics on the thickness of the nanocrystalline film target in intense, ultrashort laser–solid interaction

• Published in: Applied physics. B, Lasers and optics Lasers and optics, 2020-09, Vol.126 (9), Article 151
• Main Authors: Sarkar, Deep, Adak, Amitava, Sarkar, Subhrangsu, Shaikh, Moniruzzaman, Jana, Kamalesh, Ved, Yash M., Dey, Indranuj, Lad, Amit D., Ayyub, Pushan, Kumar, G. Ravindra
• Format: Article
• Language: English
• Subjects: Applied physics; Electron energy; Energy spectra; Engineering; Femtosecond pulsed lasers; Film thickness; Fused silica; Lasers; Nanocrystals; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Quantum Optics; Silicon dioxide; Target thickness; Temperature dependence
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-020-07499-0

We demonstrate an interesting modulation of fast electron temperature and yield as a function of the thickness of nanocrystalline coating on a dielectric target, in femtosecond, intense laser interaction with a solid target. We measure the fast electron energy spectrum for fused silica targets coated with ultrathin, nanocrystalline Cu films with thickness ranging from 30 to 100 nm and compare them with those from a planar, uncoated polished silica surface. The fast electron temperature exhibits an unexpected dependence on the film thickness, peaking at 30 and 45 nm and falling off for films with higher thicknesses. During these experiments, the size of the Cu nanograins was kept constant and only the film thickness was varied. We find that—in the low thickness limit—the target thickness acts as an additional length scale, independent of the surface topography, and needs to be separately optimized for maximizing the generation of fast electrons from high-intensity, ultrashort laser–matter interaction.