Off-resonant infrared laser action in NH3 and C2H4 without population inversion

Abstract

Several new infrared laser lines in CO2-laser-pumped NH3 and C2H4 have been observed under conditions that preclude population inversion. The emission frequency is found to be off resonant by roughly the same amount as the pump frequency, which is consistent with the theory of Raman-type transition in a coupled three-level system.