Supersonic Chemical Oxygen-iodine Laser Research Articles

Experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser

We report on detailed experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser. The laser has a 5 cm long active medium and utilizes a simple sparger-type O2(1 Δ) chemical generator and a medium-size pumping system. A grid nozzle is used for iodine injection and supersonic expansion. 25 W of cw laser emission at 1.315 µm are obtained in the present experiments. The small size and the simple structure of the laser system and its stable operation for long times make it a convenient tool for studying parameters important for high-power supersonic iodine lasers and for comparison to model calculations. The lasing power is studied as a function of the molar flow rates of the various reagents, and conditions are found for optimal operation. Good agreement is found between the experimental results and calculations based on a simple one-dimensional semi-empirical model, previously developed in our laboratory and modified in the present work. The model is used to predict optimal values for parameters affecting the laser performance that are difficult to examine in the present experimental system.

Parametric study of the gain in a small scale, grid nozzle, supersonic chemical oxygen-iodine laser

We report on experiments and model calculations of the small-signal gain and the gain profile in a grid nozzle supersonic chemical oxygen-iodine laser. The laser has a 5-cm long active medium and the gain is measured using a diode laser. The calculations are based on a simple one-dimensional semiempirical model previously developed in our laboratory. The gain is studied as a function of the molar flow rates of the various reagents and optimal conditions are found for maximum gain. In particular, an optimal value of the flow rate of I/sub 2/ is found in the experiment and explained by the present model. The small size and the simple structure of the laser combined with the simplicity of the model make the present system a useful tool for studying parameters important for high power supersonic iodine lasers. >

Spatial gain measurements in a chemical oxygen iodine laser (COIL)

The spatial distribution of small signal gain has been investigated on the RADICL device, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F=3/spl rarr/F=4 hyperfine levels of the (/sup 2/P/sub 1/2/) to (/sup 2/P/sub 3/2/) spin-orbit transition in atomic iodine was used as a small signal probe. A peak gain of 1.2%/cm was measured along the horizontal centerline of the single-slit, supersonic nozzle, which is about two times greater than measurements made on ReCOIL by Hager et al. (1988) and compares favorably with measurements made on the RotoCOIL device by Keating et al. (1990). Gain distribution was investigated under three I/sub 2/ flow conditions. Scans across the supersonic expansion indicate a gradient in gain distribution due to higher gas temperatures along the walls and mixing phenomena. >

Modeling of mixing in chemical oxygen-iodine lasers: Analytic and numerical solutions and comparison with experiments

The processes of iodine dissociation, population inversion, and lasing in the chemical oxygen-iodine laser (COIL) are affected by the mixing between the flows of oxygen and injected iodine. The effect of mixing on the operation of the COIL is studied theoretically applying a simple one-dimensional leaky stream tube model and the results are compared to available experimental data. The model enables the calculation of the iodine dissociation and the gain along the flow and of the lasing power, as a function of the iodine flow rate (nI2), the yield of singlet oxygen [O2(1Δ)] and the pressure in the cavity. Both the fraction of the dissociated iodine and the maximum gain are shown to be nonmonotonous functions of nI2. There is an optimal value of nI2, depending on the O2(1Δ) yield, the gas velocity, and the temperature in the cavity, for which the gain achieves its maximum and the iodine dissociation length its minimum. The model shows that the maximum nI2 for which lasing is possible is less than 5% of the oxygen flow rate. This result is in agreement with experimental data and cannot be explained by models based on the assumption of a premixed flow. Simple analytic expressions are derived for the optimal nI2, the characteristic length of iodine dissociation, the gain, and the lasing power. The calculated gain and lasing power are compared with available experimental results for both subsonic and supersonic COILs.

A small scale, supersonic chemical oxygen-iodine laser

A supersonic chemical oxygen-iodine laser of 5 cm long active medium has been operated utilizing a simple sparger-type O 2( 1Δ) chemical generator and a medium size pumping system. A grid nozzle was used for iodine injection and supersonic expansion. 9 W of cw laser emission at 1315 nm were obtained in the present experiments. The small size and the simple structure of the laser system and its stable operation for long periods make it a convenient tool for studying parameters important for high-power supersonic iodine lasers.

Theoretical Analysis on Supersonic Flow Chemical Oxygen-Iodine Laser Performances Using an Instantaneous Mixing Assumption.

Numerical simulation of a supersonic flow chemical oxygen-iodine laser is performed and its gain characteristics are studied. It is assumed that the flow is quasi-one-dimensional and the O2-I2 mixing takes place instantaneously at the iodine injector. The numerical results clearly show that the gas cooling by the supersonic expansion is very effective in obtaining high gain. It is shown that a small signal gain coefficient of 1.5∼2 m<-1> is attained downstream of the nozzle exit. It is also shown, however, that the temperature rise due to the chemical reactions which persist in the flow is quite detrimental to the laser performance.

Aerodynamic Characteristics of a Supersonic Flow Chemical Oxygen-Iodine Laser. Starting Characteristics of Supersonic Flow at Low Reynolds Number.

Starting characteristics of a supersonic flow are investigated experimentally in the low Reynolds number range of interest for supersonic flow chemical oxygen-iodine lasers. It is shown that the supersonic flow cannot be started in the test section of constant cross-sectional area at low Reynolds number due to the unacceptale pressure loss, even though a second throat is not utilized. The supersonic flow can be stared at higher Reynolds number with a reasonable pressure ratio which is predicted by the normal shock theory. However, the Mach number in the test section decreases rapidly along the flow due to the presence of thick boundary layers. The use of the diverging test section resuls in a lower critical Reynolds number for starting the supersonic flow and lowers the temperature, although a considerably high pressure ratio is required.