Calculation of the extreme-ultraviolet radiation conversion efficiency for a laser-produced tin plasma source

Abstract

This article presents the calculation results on the conversion efficiency (CE) of 1.064 μm laser-produced plasmas (LPPs) extreme-ultraviolet (EUV) tin (Sn) light sources with the Gaussian and a triangular-flat-topped like laser pulse temporal shapes. The computational model includes a collisional-radiative model and 1D hydrodynamics code that predicts reported experimental and theoretical results on the CE of 1.064 μm and 10.6 μm LPP EUV sources with the planar and mass-limited spherical Sn targets. The calculations for the case of a spherical target reveal that an optimum triangular-flat-topped like laser pulse generates a higher CE compared to the Gaussian pulse, especially, for the longer laser pulse duration than ≈ 30 ns. The study demonstrated that a rising intensity rate of the laser pulse has a vital role to optimize the CE as well as to prolong the in-band (13.5 ± 0.135 nm) spectral emission of a small Sn spherical target. The model predicts a ≈ 30 ns rising time duration for a linearly increasing intensity of triangular-flat-topped 1.064 μm laser pulse is necessary to obtain a maximum CE with a typical ≈ 40 μm diameter liquid Sn droplet.