Lasing degradation effects in diode-pumped alkali lasers

Abstract

Experiments on power scaling of Diode Pumped Alkali Lasers (DPALs) revealed some limiting effects, which cause output power degradation in time, alkali cell windows and gain medium contamination and damage, lasing efficiency decrease or even lasing termination. These problems can be connected to thermal effects, ionization, chemical interactions between the gain medium components and alkali cells materials. Study of all these and, possibly, other limiting effects and ways to mitigate them is very important for high power DPAL development. This paper (based on the talk presented at the SPIE Security + Defence Conference, Berlin, Germany, 10-13 September 2018) presents our results on the study of limiting effects causing lasing degradation. We performed contactless measurements of temperature rise in the gain medium of an operating DPAL based on Cs and K atoms with different buffer gases including hydrocarbons and noble gases and measured critical for degradation temperatures. In these experiments we also observed side fluorescence from the lasing gain medium, which allows studying excitation of higher energy levels because of alkali atoms ionization and recombination.