Ultrafast plasma dynamics in laser-irradiated nanowire arrays probed with an X-ray free-electron laser

Nanowire arrays are excellent nanostructured target materials for high-energy density (HED) science and applications because of their enhanced energy absorption properties. However, investigations of the spatiotemporal dynamics of laser-irradiated nanowire arrays remain limited, since conventional time-resolved diagnostics cannot capture the rapid plasma-state transitions. This study reports spatiotemporally resolved measurements of laser energy absorption and electron transport in laser-irradiated nanowire arrays using an X-ray free-electron laser (XFEL). The XFEL measurements showed that the nanowire array is promptly heated to an electron temperature of ~ 120 eV at the main-pulse interaction peak, followed by a further increase to ~ 140 eV around 10 ps, which was associated with wire collapse. The experimental results also confirmed that further enlargement of the heated area was suppressed by the restricted electron transport in nanowire arrays. These observations advance our understanding of HED plasma formation and evolution within the laser-irradiated nanowire arrays, laying a foundation for various applications.