Effect of rotational and intramode vibrational coupling on short-pulse amplification in CO2

The extraction of stored energy from a CO2-laser amplifier by a short-duration input pulse is described using a rate-equation theory. The influence of rotational and intramode vibrational energy-transfer processes is studied as a function of the energy density Einand width τpof the input pulse. By a suitable choice of normalized variables δ and for the extracted-energy and input-energy density, it is found that the results for different values of τpare interrelated by simple translations in a δ versus diagram. The characteristic curves in this diagram are nearly independent of the amplifier gain factor for high-gain systems. A comparison of the theory with experimental results of Figueira et al. shows satisfactory agreement and leads to an estimate of (1.0-3.5) 10^-6s^-1torr^-1for the rate of intra-mode vibrational-vibrational (VV) energy transfer in CO2.