An optically pumped iodine photodissociation laser has been developed and the gain-switched pulse output has been investigated. The simplified 6-level model of the iodine laser rate equations is found to be sufficient to explain the gain-switched pulse output characteristics of the laser.
The efficient flash lamp system is developed for pumping of the laser. The discharge circuit is analyzed numerically and parallel connection of the two flash tube system is employed for the double elliptical flash reflector.
Using the iodine laser oscillator designed and prepared, the mode beating phenomena in the output pulse are investigated. The beating pulse is explained by employing an assumption that several adjacent modes are excited in the resonator coherently. The ratio of the coherent modes to the total number of longitudinal modes which are excited in the cavity, is found to be up to 80% when the cavity length is 450 cm. Also the photodissociation rate is measured by using the threshold condition when the i-$C_2F_7I$ is used as active medium. The photodissociation rate is found to be about 15% for 500J electrical energy discharged in the flash lamps.
An amplifier which has the same size of the oscillator, is also designed and prepared for the determination of the extraction rate of the amplifier. The measured extraction rate is found to be 67% when the $i-C_3F_7I$ gas fill pressure is 20 torr in the amplifier tube. It is found that as the gas fill pressure increases, the extraction rate decreases.
The output power from the oscillator is found to be 1.3 MW for multimode oscillation. When the oscillator is operated on the $TEM_{oo}$ mode, the output pulse energy is 20 mJ. The pulse duration of the primary peak in the gain-switched output is about 150 nsec.
As the $TEM_{oo}$ pulse from the oscillator is amplified in the aforementioned laser amplifier the power multiplies 9.5 times, but as the gas fill pressure in the amplifier increases to 120 torr, the amplification factor is 21.5 times. However the calculation shows that the amplification factor can be as high as 43.4 and the amplified output is 5.6 MW.
