Theoretical analysis of the dynamic behavior of a fast axial flow CO2 laser amplifier

A fast-axial-flow (FAF) CO2 laser is one of the promising systems for high-power sources for machinery, welding, and medicine. The authors have experimentally observed temporal decrease of the amplified ower after discharging plasma tubes within a few minutes in the FAF CO2 laser amplifier. They first theoretically analyze the power decrease ΔP, the transient time to have stable output taust, and the small-signal gain γ by taking account of the gas flow velocity, discharge current, input intensity, and plasma length into the gain constant. Then the theoretical estimates of //d/P, taust, and γ are compared with the experimentally obtained results in the FAF (500-W) class amplifier. By curve fitting the calculated estimates to the experimental small-signal gain, the authors have known N2/N1 at tau = 0 and taust and T(0) and (Ttaust) under the discharge current Idis = 45 mA and ν = 160 m/s. Using these values as the reference information and introducing the dependences of ν and Idis on N2/N1 and T(0) and T(taust), the authors can evaluate the dependences of ν and Idis on γ, ΔP, and taust