The atomic iodine laser with approximate power of 60KW, operating at the wavelength 1.32 um by $I(5^2p_{1/2}) - I(5^2P_{3/2})$ transition, is investigated experimentally. The optical pumping using argon flash with maximum stored electric energy of 450 joule is used to induce the photolysis of $CF_3I$ molecules, and the pulsed electric discharge (0.25 μs duration) through the modified Rogowski electrode is used to produce glow discharge through $CF_3I$ medium. The entire instrumentation is made in the present research and finally the efficient lasing action is observed in the resonator by optical pumping.
The complete chemical processes, which include the photolysis of the $CF_3I$ molecule and involved to the population inversion between the two atomic states of iodine, may be described by twelve chemical formulae, and the non-linear rate equations of the iodine laser dynamics are derived by considering these chemical processes. The numerical solutions of the laser dynamics are obtained through the computer calculations.
The results show the spiking peak at very beginning of the laser pulse and the peak power output is proportional to the pressure of $CF_3I$ gas. Also, the calculation indicates the number of $I_2$ molecules, which is the dominant deactivator or quencher reducing the population of $I(5^2P_{1/2})$, increases by $t^{4.1}$ at the initial stage of optical pumping and then does by $t^{1.1}$ at the later stage.
The laser power experimentally obtained by using a Ge photodiode detector shows saturation as the pressure of $CF_3I$ gas in the resonator increases beyond approximately 40 torr. This effect is explained by the exponential absorption of the pumping radiation.
In the higher pressure of $CF_3I$ gas, the successive optical pumping gives faster decrease in laser power output, however, in a lower pressure medium the decrease in the laser power output is insignificant. The time interval between the successive optical pumping effects distinctly on the laser power output. When it is longer, the power falls slower. This is explained as the effect of decrease of the population of the quenching molecule, $I_2$. The iodine molecules formed during optical pumping and lasing period condense and solidity on the glass wall of the resonator. Further effect of the longer time interval is due to thermal relaxation time. The higher temperature attained by $CF_3I$ molecule during the pumping relaxes to the room temperature. The shorter time interval, shorter than the thermal relaxation time, increases the collision cross section between the quencher $I_2$ and the atomic iodine $I(5^2P_{1/2})$.
The effect of foreign gas is also investigated by introducing the argon gas into the medium of $CF_3I$. Argon atom quenches the $I(5^2P_{1/2})$ atom so that the decrease in the laser power output is further accelerated.
The pulsed electric discharge pumping is not satisfactory, firstly due to the instability of the glow discharge in the medium of $CF_3I$ molecule. As the molecule decomposes to various chemical ingredients, the glow discharge are found to tend to are discharge. The electric discharge pumped iodine laser is, however, much attractive, and further research efforts may be of worth.
