Specular Reflectivity and Diffuse Scattering of Plasma Mirror as a Function of Laser Intensity in Polymer Target

We present a systematic study on the optical response of plasma mirrors generated in polymer foils under ultrashort laser pulse irradiation within the non-relativistic intensity regime, reaching up to 2×1017 W/cm2. Using a Ti:sapphire system that delivers 50 fs pulses, we simultaneously measured reflection, transmission, and diffuse scattering with three energy meters for single-shot laser energies of 5, 10, 15, and 20 mJ as a function of the laser spot size on the target. The results reveal intensity-dependent variations in reflectivity, accompanied by simultaneous changes in transmission and scattering, allowing to estimate laser energy absorption by the polymer. Morphological analysis of the plasma surface suggests a significant role in modifying energy absorption, with implications for the efficiency of processes such as laser particle acceleration, nuclear fusion, and attosecond pulse generation. These findings provide critical insights into plasma mirror formation, absorption dynamics in polymers, and the potential of nanostructured polymer targets in high-intensity laser–matter interaction applications.