Simulations of plasmas driven by laser wavelengths in the 1.064—10.6 μm range for their characterization as future extreme ultraviolet light sources
We characterize the properties of extreme ultraviolet (EUV) light source plasmas driven by laser wavelengths in the λ_laser = 1.064 − 10.6 μm range and laser intensities of I_laser = 0.5 − 5 × 10^11 W cm^−2 for λ_laser = 1.064 μm. Detailed numerical simulations of laser-irradiated spherical tin microdroplet targets reveal a strong laser-wavelength dependence on laser absorptivity and the conversion efficiency of generating in-band EUV radiation. For λ_laser = 1.064 μm irradiation, the increase in in-band radiation with increasing laser intensity is offset by only a minor reduction in conversion efficiency. Radiative losses are found to dominate the power balance for all laser wavelengths and intensities, and a clear shift from kinetic to in-band radiative losses with increasing laser wavelength is identified. Yet, with increasing laser intensity, such a shift is absent. We find that the existence of a maximum conversion efficiency, near λ_laser = 4 μm, originates from the interplay between the optical depths of the laser light and the in-band EUV photons for this specific droplet-target geometry.