"Extreme" Contrast, Ultrahigh Intensity Femtosecond Laser Interaction with Solids*

In this study, we present various experimental measures of the interaction of extreme contrast (10^-18 ?), 400 nm relativistic intensity laser pulses [1] with a variety of targets- metals and

insulators; planar surfaces and those with surface structure. We make surprising observations: (a) planar surfaces are not efficient absorbers and surface structuring may be essential to

enhance coupling, (b) modulated surfaces have high absorption across many orders of intensity and (b) the ejected relativistic electrons travel in a direction counter to the expectation. For high contrast (10 ^-9 ) pulses, we present femtosecond time- resolved and micron space-resolved 2-D plasma motion [2, 3] and phase changes that include ‘nanoscopy’ of the preplasma [4], attempting a comprehensive picture of the basic physics for pulses of both contrasts and a better definition of the simulation space. Our measurements are essential in advancing the fundamental understanding of the dynamics of matter at extreme states, relevant to fusion physics as well as astrophysical scenarios.

References

[1] C. Aparajit et.al. Opt. Lett. 46, 3540 (2021); in preparation

[2] Kamlesh Jana et. al. Phys. Rev. Research 3, 033034 (2021)

[3] Kamlesh Jana et. al. AIP Advances 12, 095112 (2022)

[4] A. Dulat et al. Opt. Lett.47, 5684 (2022); in preparation