Enhanced extreme ultraviolet emission from laser-heated blow-off tin plasmas

This work investigates extreme ultraviolet (EUV) emission at 13.5 nm from laser-produced tin plasmas generated using a mass-limited laser blow-off (LBO) plume created from a 1 μm Sn foil using 1064 nm, 6 ns Nd:YAG laser pulses. The LBO method produces a low-density, spatially extended pre-plume whose mass distribution can be precisely tuned through the interpulse delay between a low-energy pre-pulse and a higher-energy main heating pulse. Experiments using EUV spectroscopy, interferometry, shadowgraphy, and retarding field ion analysis reveal that heating the LBO plume significantly enhances laser–plasma coupling and reduces self-absorption compared to conventional bulk or foil Sn targets. Optimal delays yield up to a 35% improvement in relative in-band emission intensity. Electron-density measurements show that LBO-generated plasmas form large, low-density regions favorable for efficient absorption of the heating pulse, as well as reduced density gradients. Ion diagnostics performed using a retarding field analyzer further indicate increased ion flux and reduced ion velocities at optimal delays. HELIOS-1D radiation-hydrodynamics simulations are shown to be in agreement with experimental results.