Raman gain in 12-μm NH_3 lasers

Abstract
We report the first known observation of lasing in NH3 on the aP(6, 2) transition at 12.26 μm. Emission is obtained by pumping the aR(4, 2) line with the P(34) 9-μm CO2 laser line. The frequency offset between pump and absorption line center is 5.16 GHz. This pump–emission pair was chosen to minimize the effects of ac Stark shifts and population transfer and allows us to study the Raman processes occurring in this type of optically pumped laser. We have confirmed that lasing takes place by a Raman process and obtained good agreement between theory and experimental measurements of small-signal gain.