Efficient multiline nanosecond pulse amplification in planar waveguide CO_2 amplifier for extreme UV laser-produced plasma source

摘要

In this Letter, we report on recent experimental results of a short pulse amplification at 10.6 μm wavelength required to drive a tin laser-produced plasma (LPP) extreme ultraviolet (UV) source. We report for the first time, to our best knowledge, a highly efficient pulsed amplification in a multipass amplifier built on RF-discharge-excited, diffusion-cooled CO_2, planar waveguide industrial CO_2 laser. About 2 kW of output average power was obtained from about 100 W input average power in ～15 ns pulses at 100 kHz pulse repetition frequency. As much as 60% relative extraction efficiency, as compared to continuous-wave amplification in similar conditions, and 5.8% wall-plug efficiency was recorded and believed to be the highest reported so far. An improvement of extraction efficiency by ～10% is reported when driving the amplifier with two lines of CO_2 regular band in good agreement with expectations.