Flexible CO2 laser system for fundamental research related to an extreme ultraviolet lithography source

A CO2 laser system with flexible parameters was developed for fundamental research related to an extreme ultraviolet (EUV) lithography source. The laser is a master oscillator and power amplifier (MOPA) system, consisting of a master oscillator, an externally triggered plasma switch, a preamplifier, a main amplifier, and electronic synchronization units. The laser pulse duration can be varied easily from 10 to 110 ns, with a constant peak power for pulse durations from 25 to 110 ns. The MOPA laser system can also be operated in dual-oscillator mode to produce laser pulse with pulse duration as long as 200ns and a train of laser pulses with flexible interval. The divergence of the laser beam is 1.3 times the diffraction limit. The laser intensity on the target surface can be up to 8 x 10(10) W/cm(2). Utilizing this CO2 MOPA laser system, high conversion efficiency from laser to in-band (2% bandwidth) 13.5 nm EUV emission has been demonstrated over a wide range of laser pulse durations. (C) 2009 American Institute of Physics. [doi:10.1063/1.3270257]