PIC-simulation of ultra-intense laser plasma interaction with shaped silica microtargets

Mass limited targets (MLT) in laser plasma interaction (LPI) is a reliable pathway to achieving warm and hot dense matter (WDM/HDM) states. The effects of ultra-high intensity laser light on various geometric arrangements of silica microspheres and cubes as MLT were investigated using 2D EPOCH particle-in-cell code. Multiple target configurations were used, where the laser, with 10¹⁸ W/cm² or 10²⁰ W/cm² peak intensity, 400 nm wavelength, 40 fs pulse duration and a 1 µm beam waist radius, is focused onto a collection of targets. Initial conditions were charge-neutral and room temperature (300 K). Species were set to field ionize using a semi-classical tunneling ionization model and release electrons in strong accelerating fields. For all configurations, the simulations were carried out up to 400 fs. Comparison of single versus multiple target cases show that targets not directly hit by the laser exhibit different charged particle dynamics. At 10¹⁸ W/cm² intensity, uniform electron heating was observed in the indirectly heated targets when the laser is focused onto the middle target only. Ionization of adjacent spheres with minimal dispersion is also demonstrated. At 10²⁰ W/cm² intensity, jet-like patterns of ejected charged particles are observed in multi-target configurations.