Abstract

The ability to precisely attenuate high-power pulsed CO₂ laser radiation without spatial or temporal distortion is important in many uses ranging from micro-machining to threshold measurements. Attenuation methods using Brewster stacks, gratings or frustrated internal reflection rely on the polarization of the incident laser radiation. The use of absorbing flats (such as CaF₂ or LiF), although polarization independent, allows only discrete attentuation. Additionally, such techniques are not readily scalable to large aperture, high energy laser beams. A possible solution is the use of gas attenuators^1-3 However, for a large dynamic range in attenuation over reasonable path lengths, the requirement of a suitably large absorption cross-section inevitably leads to saturation and consequent beam distortion at relatively moderate laser intensities. We report a new technique that uses a binary mixture of SF₆ and He to overcome these limitations and permits linearly variable, distortion-free attenuation of high-power pulsed TEA CO₂ laser radiation (at 10.6 µm).

© 1992 Optical Society of America