Experimental measurement of ionization degree in diode-pumped rubidium laser gain medium

We use optogalvanic method to measure the ionization degree in the hydrocarbon-free rubidium DPAL gain medium. The results show that the ionization degree increases as pump intensity and helium pressure increase, and presents rollover as rubidium concentration increases. A maximal ionization degree of ∼6.45×10(-6) has been obtained with pump intensity of 0.82  kW/cm2, temperature of 150°C and helium pressure of 500 Torr. Theoretical estimation shows that energy pooling is the main process rather than photoexcitation for the subsequent ionization processes.