Standing-Wave Forward-Backward Gain Asymmetry in Optically Pumped Gas Lasers

Abstract
A new type of forward-backward asymmetry is reported for the 119-μm emission from a linear-cavity CH3OH laser, near-resonantly pumped by a continuous-wave CO2 laser. The observed asymmetry is related to a strong traveling-wave pump field and also saturating standing-wave-generated fields, a situation typical for most optically pumped linear-cavity gas lasers. A simple interpretation of the experimental results is given in terms of multiphoton processes involving one pump photon and several generated photons.