Measurement and modeling of ionization in a cesium diode pumped alkali laser (DPAL)

We report direct measurement of the laser induced ionization rate of cesium, relevant for a Diode Pumped Alkali Laser (DPAL), via application of an ion chamber diagnostic. Computer simulation predictions of the multi-step ionization mechanism will be compared against measured ionization rates. The results will be shown to accurately predict the low level of ionization to within an order-of-magnitude, as well as relative trends across pump intensities of 8–100 W/cm \(^2\) $_{}^2$ and cesium densities of 0.3–2.2 \(\times\) $\times$ 10 \(^{12}\) $_{}^{12}$  cm \(^{-3}\) $_{}^{-3}$ . Comparison of fluorescence from 7P energy states with known direct excitation pathways and fluorescence from highly-excited 7D states suggests rapid mixing of high energy states. The application of 300 V on the ion chamber electrodes (sufficient to cause current saturation) has minimal impact on fluorescence. This supports the notion that Rydberg states are populated via a neutral particle process, rather than via electron/ion recombination, as has been previously suggested.