Characterization of charge state distributions in Near-Infrared Laser-Driven tin plasmas for efficient EUV generation

• The spatiotemporal evolution of charge state distributions in laser-produced tin plasmas was quantitatively modeled using radiation-hydrodynamic and non-local thermodynamic equilibrium simulations. • A mean charge state of ∼ 12.5 was identified as optimal for maximizing Sn 11+ –Sn 14+ ion populations responsible for 13.5-nm EUV emission. • Simulated short-wavelength (7–10 nm) spectra showed strong agreement with experimental results under CE-maximizing conditions, validating the predictive model. • Flat-top laser pulse shaping suppressed over-/under-ionization and enhanced Sn 11+ –Sn 14+ ion production by up to 45 % compared to Gaussian pulses. • These results provide essential guidance for optimizing EUV light sources without requiring detailed atomic modeling of 13.5-nm transitions. In this paper, the charge state distributions of extreme ultraviolet (EUV) light source plasmas produced by near-infrared-wavelength lasers are systematically characterized. The spatiotemporal properties of laser-irradiated planar tin targets are examined using radiation-hydrodynamic simulations and non-local thermodynamic equilibrium calculations. Focusing on the distributions of Sn 11+ –Sn 14+ ions, which are primarily responsible for “in-band” EUV emissions, a mean charge state of 12.5 is identified as the optimal ionization level for efficient EUV generation. This prediction is consistent with the experimental observation by Behnke et al. (2021) of short-wavelength spectra in the 7–10 nm range, where the contributions of the Sn 11+ –Sn 14+ ions are well identified. Simulations further reveal that spatially and temporally uniform pulses more efficiently achieve the optimal mean charge state, producing up to 45 % more Sn 11+ –Sn 14+ ions than Gaussian pulses of the same energy. These findings provide foundational insights for advancing laser-driven EUV light sources for industrial applications.