18 March 2016 Development of a non-contact diagnostic tool for high power lasers
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Abstract
High power lasers in excess of 1 kW generate enough Rayleigh scatter, even in the NIR, to be detected by silicon based sensor arrays. A lens and camera system in an off-axis position can therefore be used as a non-contact diagnostic tool for high power lasers. Despite the simplicity of the concept, technical challenges have been encountered in the development of an instrument referred to as BeamWatch. These technical challenges include reducing background radiation, achieving high signal to noise ratio, reducing saturation events caused by particulates crossing the beam, correcting images to achieve accurate beam width measurements, creating algorithms for the removal of non-uniformities, and creating two simultaneous views of the beam from orthogonal directions. Background radiation in the image was reduced by the proper positioning of the back plane and the placement of absorbing materials on the internal surfaces of BeamWatch. Maximizing signal to noise ratio, important to the real-time monitoring of focus position, was aided by increasing lens throughput. The number of particulates crossing the beam path was reduced by creating a positive pressure inside BeamWatch. Algorithms in the software removed non-uniformities in the data prior to generating waist width, divergence, BPP, and M2 results. A dual axis version of BeamWatch was developed by the use of mirrors. By its nature BeamWatch produced results similar to scanning slit measurements. Scanning slit data was therefore taken and compared favorably with BeamWatch results.
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Jed A. Simmons, Jed A. Simmons, Jeffrey L. Guttman, Jeffrey L. Guttman, John McCauley, John McCauley, "Development of a non-contact diagnostic tool for high power lasers", Proc. SPIE 9741, High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications V, 97410N (18 March 2016); doi: 10.1117/12.2213605; https://doi.org/10.1117/12.2213605
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