Development of an efficient XUV 64nm source using resonant third harmonic generation

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Any extreme ultraviolet (XUV) laser source for industrial applications, whose wavelength is shorter than 100nm, has not been developed. In this project, we want to develop an XUV coherent source which can be used for industrial application, based on an ArF excimer laser with high repetition rate. XUV radiation at 64nm can be efficiently generated by two-photon resonant third harmonic generation. When an ArF laser beam is focused into a hydrogen gas jet and the wavelength is tuned at one of the rotational-vibrational line of H_2, XUV radiation is enhanced. We investigated the optimization of the excimer laser fluence, the density and the shape of H_2 gas jet. Theoretical calculation, including the absorption of ionization and the phase matching, shows that a gas jet with a profile of thin along the optical axis and wide in the cross section is preferable.We tried to determine the absolute energy of the XUV radiation by two methods : one is the ion counting when XUV photons are absorbed by an Ar jet, and the other is the absolute calibration of the spectroscopic sensitivity of the detecting system. As the result, XUV energy of 1-4muJ/pulse was confirmed to be generated, and we successfully finished the project.