Dynamics of laser-produced Sn microplasma for a high-brightness extreme ultraviolet light source

The effect of laser focal spot diameters of 26 and 150 mu m on 13.5 nm extreme ultraviolet (EUV) radiation is investigated. Simulations show that the smaller spot size has a shorter electron plasma density scale length and deeper and denser laser energy deposition region. This results in additional time required for plasma expansion and radiation transport to efficiently emit EUV light. This is experimentally observed as an increase in the delay between the EUV emission and the laser pulse. The shorter scale length plasma reabsorbs less EUV light, resulting in a higher conversion efficiency, smaller and slightly brighter light source. (C) 2011 American Institute of Physics. [doi:10.1063/1.3589359]