2018/07/20 by Amitava Adak, Amit D. Lad, Adak, Amitava +9
Engineering · Medicine · #Laser-induced spectroscopy and plasma #Ocular and Laser Science Research #Laser Material Processing Techniques
paper · pdf · doi:10.48550/arxiv.1807.07772
The basic understanding of high-intensity femtosecond laser absorption in a\nsolid is crucial for high-energy-density science. This multidimensional problem\nhas many variables like laser parameters, solid target material, and geometry\nof the excitation. This is important for a basic understanding of intense\nlaser-matter interaction as well for applications such as `plasma mirror'.\nHere, we have experimentally observed high-intensity, high-contrast femtosecond\nlaser absorption by an optically polished fused silica target at\nnear-relativistic laser intensities (\∼1018 W/cm2). The laser\nabsorption as a function of angle of incidence and incident energy is\ninvestigated for both p- and s-polarized pulses in detail, providing a\nstrong indication of the presence of collisionless processes. At an optimum\nangle of incidence, almost as large as 80% of the laser (p-polarized) energy\ngets absorbed in the target. Such a high percentage of absorption at\nnear-relativistic intensities has not been observed before. At smaller angles\nof incidence the high reflectivity (e.g. about 60 - 70% at 30^\∘\nincidence) indicate that, this study is fundamentally relevant for plasma\nmirrors at near-relativistic intensities.\n