Investigation of a thulium vapor laser

New laser emission lines were obtained and identified when thulium vapor was excited by a pulsed gas discharge. The spectrally integrated specific laser output energy in the visible and near infrared regions was 20 μJ/cm³. An investigation was made of the behavior of infrared laser radiation pulses under different conditions, leading to the proposal that the transfer of excitation from closely spaced resonant levels of the thulium atom in the presence of atom–atom collisions is the mechanism for pumping the upper active levels.