Transient gain phenomena and their improvement in a fast-axial flow CO2 laser amplifier.

Abstract

The present paper reviews our recent work on transient gain phenomena caused by both thermo & gas dynamic cooling mechanism and dissociation of CO2 molecules in a fast-axial flow (FAF) CO2 laser amplifier. Taking into account a time-dependent gas temperature T and an inverted population n2/n1, we theoretically formulate a transient gain as functions of the gas-flow velocity ν and the discharge current Idis including their spatial distributions along the radial direction from the plasma-tube axis to explain the transient power-decrease ΔP and the transient time tst required to be a stable value with respect to a plasma length l and an input probe power Pin Theoretical calculations are in good agreements with, corresponding experimental results. Possibilities for improving the above transient behavior are also demonstrated by cooling a plasma-tube wall and by use of an Au catalyst.