The effects of atomic rubidium vapor on the performance of optical windows in Diode Pumped Alkali Lasers (DPALs)

Diode Pumped Alkali Lasers (DPALs) suffers from damage to its optical windows due to atomic alkali exposure. DPALs are of great interest since they can combine multiple lasers to achieve higher laser output power, scalable to megawatts, with very high quantum efficiency. However before scaling to higher laser output beam power, damage to the optical windows from atomic alkali exposure in the gain medium has to be addressed. A DPAL emulator chamber was constructed for the purpose of evaluating different optical windows in a representative hot alkali rich environment typical of a DPAL gain cell. Sample optical windows of fused silica, alumina, magnesium fluoride and calcium fluoride were exposed in the DPAL emulator in order to qualitatively and quantitatively demonstrate and assess the damaging effects of the atomic rubidium vapor on the optical windows. Methodologies to examine the damage were developed for comparing exposed and unexposed optical windows. We found that damage to the optical windows due to the atomic rubidium can be quantified by means of changes in laser energy transmission through the optical window after rubidium exposure.

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► Exposure of optical windows in a Diode Pumped Alkali Lasers (DPALs) emulator.
► Quantification of atomic rubidium damage of optical windows.
► Changes in laser optical transmission due to atomic rubidium diffusion.
► Dual beam intensity monitoring transmission, absorption and reflection at optical windows.
► Surface roughness and damage to optical windows due to atomic rubidium.