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 Nd³⁺-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 μJ, 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 %.