A Two-Photon Optically Pumped Molecular Gas Visible Laser

Recent investigations of the multiphoton ionization (MPI) spectrum of gaseous ammonia have led to the discovery of a novel two-photon pumped molecular gas electronic transition laser. Resonant, two-photon electronic excitation of NH3 in the near uv (~305 nm) leads to the first observation of fluorescence from NH3 excited states (B and C'), and, at higher pressures, to lasing action (~570 nm) between numerous C' and A state vibronic levels. A frequency-doubled Nd:YAG pumped dye laser (a few mJ) is focused into a cell containing NH3 (or ND3). Stimulated emission is observed in the forward and backward direction at NH3 pressures greater than -200 torr, without external mirrors to provide feedback. Conversion efficiencies (output NH3 pulse energy/input pulse energy) as high as 2% have been observed.