Generation of collimated extreme ultraviolet radiation by single-photon process

Abstract

Generating laser with short wavelength is a bottleneck problem in laser technology. The current applicable table-top extreme ultraviolet (EUV) lasers are all generated by multi-photon process with low efficiency. By utilizing metastable helium atoms excited by microwave and irradiated by a resonant laser, here we report the development of 58.4 nm collimated radiation by single-photon-excitation related anti-Stokes Raman scattering (ASRS). The conversion efficiency is much higher than that of high harmonic generation (HHG). The same divergence of 1.4 mrad as that of excitation laser indicates its stimulating character. Our results show an applicable path towards up-conversion by single-photon process to generate table-top EUV lasers.