We demonstrated enhancement of in-band conversion efficiency (CE) at 13.5nm of the extreme ultraviolet (EUV) emission from a tin (Sn) cavity target irradiated by a CO2 laser pulse. Whereas a planar Sn target produced an in-band CE of around 2%, the use of cavity targets significantly enhanced the EUV emission energy and the EUV CE. An EUV CE of 4% was observed for a Sn cavity target with a depth of 200μm which is one of the highest values ever reported.

The effect of laser focal spot diameters of 26 and 150 m on 13.5 nm extreme ultraviolet ͑EUV͒ radiation is investigated. Simulations show that the smaller spot size has a shorter electron plasma density scale length and deeper and denser laser energy deposition region. This results in additional time required for plasma expansion and radiation transport to efficiently emit EUV light. This is experimentally observed as an increase in the delay between the EUV emission and the laser pulse. The shorter scale length plasma reabsorbs less EUV light, resulting in a higher conversion efficiency, smaller and slightly brighter light source.

We demonstrated a fivefold reduction in Sn debris deposited on small Mo∕Si multilayer mirrors from a Sn planar target by applying a static magnetic field of 1T. The debris reduction is attributed to the decrease of more than three orders in the number of ions that reach the sample mirror due to their interaction with the applied magnetic field that guides the ions away from the mirror. The remaining deposition is due to neutral Sn atoms that do not interact with the applied magnetic field.

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We demonstrated efficacy of a CO2-laser-produced xenon plasma in the extreme ultraviolet (EUV) spectral region at 13.5nm at variable laser pulse widths between 200ps and 25ns. The plasma target was a 30μm liquid xenon microjet. To ensure the optimum coupling of CO2 laser energy with the plasma, they applied a prepulse yttrium aluminum garnet laser. The authors measured the conversion efficiency (CE) of the 13.5nm EUV emission for different pulse widths of the CO2 laser. A maximum CE of 0.6% was obtained for a CO2 laser pulse width of 25ns at an intensity of 5×1010W∕cm2.