Influence of finite absorption in transmission optics on the propagation of high average-power pulsed CO2 laser beams

Stephanus P. van Heerden; Wouter Klopper; Francois J. Prinsloo; Andrew Forbes

doi:10.1117/12.259937

20 November 1996 Influence of finite absorption in transmission optics on the propagation of high average-power pulsed CO₂ laser beams

Stephanus P. van Heerden, Wouter Klopper, Francois J. Prinsloo, Andrew Forbes

Author Affiliations +

Proceedings Volume 2870, Third International Workshop on Laser Beam and Optics Characterization; (1996) https://doi.org/10.1117/12.259937
Event: Third International Workshop on Laser Beam and Optics Characterization, 1996, Quebec City, Canada

Abstract

The development of a high repetition rate TEA-CO₂ laser chain has a number of difficulties that must be overcome. One of these difficulties is to predict the free space propagation of the beam. A low energy (approximately 100 mJ/pulse), high-quality, carbon-dioxide beam is amplified in a number of carbon-dioxide amplifiers to more than 1 J per pulse. On propagation through the amplifier chain the primary beam encounters several transmission optics. It was found that the beam parameters of the primary beam change dramatically for high repetition rate operation (greater than 100 Hz). The alteration in beam parameters is brought about by thermal expansion and refractive index variations known as thermal lensing. This phenomenon is caused by the thermal gradient introduced to an optic by absorption of a laser beam with a Gaussian profile. Thermal lensing caused by the aforementioned laser system in transmission optics was investigated. The influence of several types of transmission optics in the amplifier chain was studied and compared. It was found that the use of a specific substrate (KCl or ZnSe) is determined by the position in the chain. A marked increase in thermal lensing effects was observed with damaged or contaminated optics.

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Stephanus P. van Heerden, Wouter Klopper, Francois J. Prinsloo, and Andrew Forbes "Influence of finite absorption in transmission optics on the propagation of high average-power pulsed CO₂ laser beams", Proc. SPIE 2870, Third International Workshop on Laser Beam and Optics Characterization, (20 November 1996); https://doi.org/10.1117/12.259937

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