Kinetics of Higher Lying Rubidium States after Pulsed Excitation of the D2 Transition in the Presence of Helium
Technical Report,01 Sep 2014,24 Mar 2016
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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The Diode Pumped Alkali Laser DPAL is a high power, three-level laser system that employs diode bars to optically excite an alkali metal vapor. It lases along the D1 transition, between the two lowest energy levels, 2P12 and 2S12. Higher lying energy states are produced at higher population density via energy pooling and multiphoton processes. Pulsed laser excitation of rubidium at approximately 1 MWcm2 has been studied at helium pressure up to 900 Torr. Emissions from energy states as high as 82D suggests modest ionization, though these intensities decrease drastically at buffer gas pressures above 250 Torr. Blue emission from the 62P-52S12 transition and red emission from the 52D-52P transition indicate population in these upper states that persists at all helium pressures used in this experiment. A basic kinetic model was created to describe the concentration at these higher lying states. Optical trapping is severe at temperatures above 450 K. Diffusion of the rubidium is very slow, requiring mixing times exceed 45 minutes.
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