Excitation Mechanisms in Pulsed CO2 Lasers

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Abstract
Experimental studies were carried out on laser systems to investigate the excitation mechanisms of the upper laser level (0001) of carbon dioxide in an electrical discharge, and the parts played by helium and nitrogen in mixed systems. Used as constituent gases were carbon dioxide, carbon dioxide‐nitrogen, and carbon dioxide‐helium. Pulsed electrical excitation was used with an arrangement for varying the time delay between the discharge pulse and the alignment of a Q‐switch mirror. The upper‐level‐to‐ground radiation was observed from the side of the tube to study the behavior of the upper level following the current pulse and when the upper level population is suddenly decreased by the Q‐switch. It is concluded that the primary excitation mechanism is electron impact for pure carbon dioxide. Nitrogen is shown to contribute by acting as a storage mechanism for energy prior to resonant transfer, and a value of 1.6×104 sec−1 Torr−1 was obtained for the rate constant of the N2→CO2 vibrational energy transfer process. Helium was found to contribute to increased output primarily through causing a favorable shift in electron temperature.

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