Enhancing the conversion efficiency of extreme ultraviolet light sources using a 2 µm wavelength laser

Abstract In this study, we use the FLASH radiation hydrodynamic code and the FLYCHK atomic code to investigate the energy conversion and spectra associated with laser–Sn target interactions with 1 and 2 µ m wavelength lasers. We found that the conversion efficiency (CE) reached as much as 3.38% with the 2 µ m laser, which is 1.48 percentage points higher than the 1 µ m laser (CE = 1.9%). In addition, we analyzed the contribution of dominant ionization states to the emission spectrum for both lasers. We observed that the growths of the out-of-band emission eventually led to a broadening of the spectrum, resulting in a reduction of spectral purity for the 1 µ m laser. By contrast, the emission main peaks were all centered near 13.5 nm for the 2 µ m laser, which is beneficial for efficient emission of light with a 13.5 nm wavelength (relevant for nanolithographic applications).