Synchronous, mode-locked pumping of gas lasers

Abstract

The generation of mode-locked far-infrared pulses by synchronous, mode-locked optical pumping by CO2 lasers is demonstrated for the first time. The gain bandwidth implied by the observed short pulses (<1 nsec) exceeds the homogeneous linewidth of 40 MHz (T2 = 8 nsec) under the experimental conditions and is attributed to an effective inhomogeneous broadening in molecules with a K-multiplet structure such as 12CH3F and also to the presence of near-resonant stimulated Raman emission from each frequency component of the pump. This implies that the duration of pulses generated in low-pressure gases by this technique is determined by the greater of the pumping-pulse bandwidth or the linewidth of the lasing transition.