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

Benjamin Oliker

Copyright © 2024, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature

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Abstract

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/cm² and cesium densities of 0.3–2.2 x 10¹² cm^-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.