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

The extraction of stored energy from a CO
2
-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
in
and width τ
p
of the input pulse. By a suitable choice of normalized variables δ and
E_{in}/E_{sat}
for the extracted-energy and input-energy density, it is found that the results for different values of τ
p
are interrelated by simple translations in a δ versus
E_{in}/E_{sat}
diagram. The characteristic curves in this diagram are nearly independent of the amplifier gain factor
\exp (\alpha_{0}L)
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
^-6
s
^-1
torr
^-1
for the rate of intra-mode vibrational-vibrational (VV) energy transfer in CO
2
.