Lasing on Molecular Nitrogen Ions in Laser Plasma

The authors study characteristics of lasing on molecular nitrogen ions in laser plasma created by a femtosecond radiation pulse. The maximum intensities at wavelengths of 391.4 and 427.8 nm are observed at nitrogen pressures of 30 and 500 mbar, respectively. The divergence of radiation is tens mrad and close to geometric. The pulse length at a wavelength of 391.4 nm varies from 1.83 to 3.5 ps upon changing the focal length of the lens from 15 to 40 cm.