A novel algorithm of compensation for repetitively-pulsed laser beam wandering at propagation paths, caused by the atmospheric turbulence and mirror vibrations has been proposed and verified in experiments with a TE-C02 laser. The algorithm is based on the precise temporal control of triggering each of the TB-laser pulses at the moments when the auxiliary probe cw-laser beam modified by a modal-type adaptive optics system and having exactly the same wavefront profile, as the pulsed radiation, hits the remote object (retroreflector in the pre-set point at the path exit) by its brightest speckle.
Recent studies of fundamental issues of target material format and laser radiation parameters 1,2 have revealed the attractiveness of LPP EUV source technology based on Sn target and multi-kW CO 2 laser driver. In recent work 3 we have reported 8kW of average power at 100kHz repetition frequency and 20ns pulse duration produced by our MOPA CO 2 laser driver built on a chain of Fast Axial Flow (FAF) amplifiers. However, the oscillator power is insufficient to saturate the input stages and significant amount of available laser energy (>80%) is untapped. In this paper we report a step towards an improvement of laser driver power and efficiency. For the first time, to our knowledge, the performance of a novel multi-pass pre-amplifier based on RF-excited slab waveguide CO 2 laser technology has been numerically modeled. The calculations show the feasibility of this approach. We carried out amplification experiments to validate the numerical model. In our experiments we have obtained power gain of 10 at 13-pass configuration from a slab of 60x600mm2 geometry at 20ns pulse length and 100kHz repetition frequency at diffraction-limited output and no selfoscillation. The experiment has validated the numerical model, which will be used at this stage to design and optimize a pre-amplifier for our current FAF amplifier chain. Furthermore, these results enable us to design and optimize next generation of LPP laser driver based entirely on compact slab-waveguide amplifiers. *k.m.nowak@euva.or.jp; phone +81-463-35-9392; fax +81-463-35-9352; http://www.euva.or.jp
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.