Design and construction of a pulsed TEA/CO₂ laser and its synchronous coupling to a ruby laser

Case, Gary Milton (1974) Design and construction of a pulsed TEA/CO₂ laser and its synchronous coupling to a ruby laser. Masters thesis, Memorial University of Newfoundland.

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Abstract

A 3-metre pulsed TEA/CO₂ laser, producing 10.6 μm radiation, was constructed, and its output characteristics investigated. The laser was of the helical pin electrode configuration with nominal 1000-Ω resistors at the cathode, and thus operated in the TEM₀₀ mode. The front laser window was a plane germanium mirror with 65% reflectivity, while the back window was a spherical silicon mirror with a radius of curvature of 10 m and a reflectivity of 99.4%. Input energy was supplied by a 0-30 KV power supply utilizing a triggered .03 μF capacitor which provided the pulsing mechanism for the laser. Using a gas mixture of 88% He, 6% N₂, and 6% CO₂, the peak power at 30 KV was approximately 2.4 MW and the output energy more than .5 J, effecting an efficiency of almost 4%. An image converter streak camera and a giant pulse ruby laser were simultaneously synchronized to the TEA/CO₂ laser. The purpose of this synchronization was to provide a system which could later be used to investigate stimulated ruby laser light scattering in CO₂ laser-induced plasmas. Synchronization was achieved with the aid of streak photographs of the plasmas. Plasmas in air were easily obtained using germanium lenses of focal lengths of up to 18 cm. Preliminary measurements were also made on the streak camera photographs which showed that the CO₂ laser-induced plasma expanded toward the laser with a velocity on the order of 10⁶ cm sec⁻¹. Also, the size of the plasma was found to increase when the ruby laser was focused on the plasma and fired simultaneously with the TEA/CO₂ laser.

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