IR laser oscillation on caesium and rubidium atomic transitions upon pumping to high-lying energy levels

Laser oscillation is obtained in caesium and rubidium atoms with wavelengths in the range of 2 – 5.5 μm under pumping to high-lying energy levels. Longitudinal resonant pumping is implemented using the second harmonic of radiation from an optical parametric oscillator. The pump wavelength is tuned over discrete levels from 8P to 10P in caesium atoms and from 6P to 8P in rubidium atoms. The width of the pump radiation spectrum is 12 cm^–1. When caesium atoms are pumped, the pump pulse energy is no more than 10 mJ; when rubidium atoms are pumped, it does not exceed 3 mJ. The pulse repetition rate is 10 Hz. The maximum output energy of IR laser radiation upon pumping the 9P_3/2 level of caesium atoms is about 100 μJ at a cell temperature of ~170 °C, while the efficiency of pump conversion into radiation energy with a wavelength l ~ 3.1 mm turns out to be ~1%. For rubidium atoms, an estimate of the output energy of IR radiation gives a value of ~80 μJ at a cell temperature of 180 °C, which corresponds to an energy efficiency of ~2.7%.