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 E/sub in/ and width tau/sub p/ of the input pulse. By a suitable choice of normalized variables delta and E/sub in//E/sub sat/ for the extracted-energy and input-energy density, it is found that the results for different values of tau/sub p/ are interrelated by simple translations in a delta versus E/sub in//E/sub sat/ diagram. The characteristic curves in this diagram are nearly independent of the amplifier gain factor exp (α0L) 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) 106 s-1 torr-1 for the rate of intramode vibrational-vibrational energy transfer in CO2