Two-photon optical pumping of NH3 in a multipass cell

A multipass cell was used in optical pumping of ammonia molecules by CO₂ laser radiation. Several new lasing lines were observed in the case of two-photon optical pumping of the NH₃ molecule at wavelengths in the range 16–35 μ. The output power of the various lines was in the range 10–50 kW. The divergence of the resultant radiation was diffraction-limited. A theoretical study was made of the two-photon pumping process. A stable (on the frequency scale) maximum was found in the gain profile of the output radiation. It was concluded that it should be possible to increase the energy and extend the emission spectrum of an ammonia laser pumped by doublephoton absorption.