Eyal Lebiush

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 ...

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(1Δ) 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. >

O2(1Δ) generation in a bubble column reactor for chemically pumped iodine lasers : experiment and modeling

O2(1Δ)is generated in a bubble column reactor by the reaction between chlorine diluted in inert gas and a basic hydrogen peroxide solution. It is fed to an oxygen‐iodine laser system designed to operate under supersonic conditions. The O2(1Δ) yield is measured as a function of the time elapsed from the onset of bubbling, type of diluent, and molar flow rate of chlorine and diluent. The yield when the chlorine is diluted with helium is significantly higher than when diluted with argon. This is explained as a consequence of the shorter residence time of the mixtures with helium where the molecular weight is smaller. A model that accounts for realistic physical and chemical processes in this system is presented. The model is divided into two stages which together describe the processes that occur between the reactor inlet and the measuring point of the O2(1Δ) (before the supersonic nozzles). The first stage describes the processes occurring in the solution. It employs the film model for a fast reaction regim...

A small scale, supersonic chemical oxygen-iodine laser

Abstract A supersonic chemical oxygen-iodine laser of 5 cm long active medium has been operated utilizing a simple sparger-type O 2 ( 1 Δ) 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.

Influence of the pump-to-laser beam overlap on the performance of optically pumped cesium vapor laser.

Experimental and theoretical study of the influence of the pump-to-laser beam overlap, a crucial parameter for optimization of optically pumped alkali atom lasers, is reported for Ti:Sapphire pumped Cs laser. Maximum laser power > 370 mW with an optical-to-optical efficiency of 43% and slope efficiency ~55% was obtained. The dependence of the lasing power on the pump power was found for different pump beam radii at constant laser beam radius. Non monotonic dependence of the laser power (optimized over the temperature of the Cs cell) on the pump beam radius was observed with a maximum achieved at the ratio ~0.7 between the pump and laser beam radii. The optimal temperature decreased with increasing pump beam radius. A simple optical model of the laser, where Gaussian spatial shapes of the pump and laser intensities in any cross section of the beams were assumed, was compared to the experiments. Good agreement was obtained between the measured and calculated dependence of the laser power on the pump power at different pump beam radii and also of the laser power, threshold pump power and optimal temperature on the pump beam radius. The model does not use empirical parameters such as mode overlap efficiency and can be applied to different Ti:Sapphire and diode pumped alkali lasers with arbitrary spatial distributions of the pump and laser beam widths.

Optically pumped Cs vapor lasers: pump-to-laser beam overlap optimization

We present the results of an experimental study of Ti:Sapphire pumped Cs laser and theoretical modeling of these results, where we focused on the influence of the pump-to-laser beam overlap, a crucial parameter for optimizing the output laser power. The dependence of the output laser power on the incident pump power was found for varying pump beam cross-section widths and for a constant laser beam. Maximum laser power > 370 mW with an optical-to-optical efficiency of 43% and slope efficiency ~55% was obtained. Non monotonic dependence of the laser power and threshold power on the pump beam radius (at a given pump power) was observed with a maximum laser power and minimum threshold power achieved at the ratio ~0.7 between the optimal pump beam and laser beam radius. A simple optical model of the laser, where Gaussian spatial shapes of the pump and laser intensities in any cross section of the beams were assumed, was compared to the experiments. Good agreement was obtained between the measured and calculated dependence of the laser power on the incident pump power at different pump beam radii and of the laser power, threshold power and optimal temperature on the pump beam radius. The model does not use empirical parameters such as mode overlap efficiency but rather the pump and laser beam spatial shapes as input parameters. This model can be applied to different optically pumped alkali lasers with arbitrary spatial distributions of the pump and laser beam widths.

Experimental and theoretical study of the performance of optically pumped cesium vapor laser as a function of the pump-to-laser beam overlap

We report on the results of an experimental study of Ti:Sapphire pumped Cs laser and theoretical modeling of these results, where we focused on the influence of the pump-to-laser beam overlap, a crucial parameter for optimizing the output laser power. Non monotonic dependence of the laser power (optimized over the temperature) on the pump beam radius was observed with a maximum achieved at the ratio ~ 0.7 between the pump and laser beam radii. The optimal temperature decreased with increasing pump beam radius. Maximum laser power > 370 mW with an optical-to-optical efficiency of 43% and slope efficiency ~ 55% was obtained. A simple optical model of the laser, where Gaussian spatial shapes of the pump and laser intensities in any cross section of the beams were assumed, was compared to the experiments. Good agreement was obtained between the measured and calculated dependence of the laser power on the pump power at different pump beam radii and also of the laser power, threshold pump power and optimal temperature on the pump beam radius. The model does not use empirical parameters such as mode overlap efficiency but rather the pump and laser beam spatial shapes as input parameters. The present results combined with results of the application of the model to K DPAL and Ti:Sapphire pumped Cs laser, indicate that the model can describe the operation of different optically pumped alkali lasers with arbitrary spatial distributions of the pump and laser beam widths.

Parametric studies of a small-scale supersonic chemical oxygen-iodine laser (COIL)

Parametric studies of the gain and the power of a small scale supersonic chemical oxygen- iodine laser are presented. The laser is of 5 cm long active medium, and utilizes a simple sparger-type O2(1(Delta) ) chemical generator and a medium size pumping system. A grid nozzle is used for iodine injection and supersonic expansion. 45 W of CW laser emission at 1315 nm are 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 and for comparison to model calculations. The gain and the lasing power are 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 1D 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.

Effect of mixing on iodine dissociation, population inversion and lasing in chemical oxygen-iodine lasers

A simple, one-dimensional leak flow tube model was used to calculate the effect of mixing on the performance of chemical oxygen-iodine lasers (COIL). Both the maximum gain and the characteristic length of the iodine dissociation are shown to be nonmonotonic functions of the iodine flow rate, nI2. The maximum nI2 for which lasing is possible is less than 1 - 2% of the oxygen flow rate. This is in agreement with experimental data and is not explained by models assuming premixed flows. The present model was applied to calculations of the performance of supersonic COILs.