Near-IR lasing in caesium vapour

Lasing in caesium vapour is obtained at λ ∼ 3 μm (transitions 7P 3/2 → 7S 1/2 and 7P 1/2 → 7S 1/2 ). Longitudinal pumping is performed by the second harmonic of a parametric oscillator pumped by the second harmonic of a Nd 3+ -doped garnet laser. The pump wavelength corresponds to the 6S 1/2 → 7P 3/2 and 6S 1/2 → 7P 1/2 transitions of caesium atoms. The pump radiation has a spectral width of 12 cm −1 , a pulse energy of 10 mJ, and a pulse repetition rate of 10 Hz. The IR laser pulse energy at a vapour cell temperature of 155 °C is 100 μJ. The efficiency of pump energy conversion to the laser radiation energy at λ ∼ 3 μm is ∼1.5%.