A laser amplifier (30cm long) for the 1.315 μm laser output from the iodine photodissociation laser oscillator is designed, and its characteristics are investigated. The output energy of the pulsed oscillator fed into the amplifier is 20 mJ for $\mbox{TEM}_{oo}$ single mode, using gaseous $i-C_3F_7I$. The population inversion ratio and the energy extraction efficiency of the gaseous $i-C_3F_7I$ are measured by varing gas pressure of laser tube in the amplifier and delay time between the oscillator and the amplifier. The variable delayed trigger pulse generator is constructed to controll the delay time in this experiment.
The maximum output energy extracted from the amplifier is found to be 430 mJ and the energy gain of this amplifier is $G_e=8.3$, at the gas pressure 100 torr and the delay time 5 μsec, which is neither a large signal amplification nor a small signal amplification.
Population inversion ratio 0.15 is obtained from the threshold condition in the low gas fill pressure ($\leqq$60 torr). The maximum energy extraction efficiency is 59% at 20 torr. This result is in agreement with the theoretical value at 20 torr, however it deviates markedly as the gas pressure increases.
