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Proceedings Paper

Band-stop angular filtering based on volume Bragg gratings. (Conference Presentation)

Paper Abstract

The uniform near-field distribution and focusing characteristics of laser beam, which is related with the spatial frequencies in laser beams, are very important for high power laser applications, such as laser processing and laser fusion. The traditional pinhole filter can be used to improve the near-field uniformity, but may lead to the pinhole-closure and back-reflection. The angular filter based on transmitting volume Bragg gratings (TBGs) recorded in the photo-thermorefractive (PTR) glass could be used to improve the near-field beam quality. However, the incident beam must satisfy the Bragg condition and the optical axis of filtered beam is deflected, which makes the laser system very difficult to align. The band-stop angular filter with two TBGs may be a good method to solve the above problems.

In this paper, the band-stop angular filtering is performed and characterized. The band-stop angular filtering is demonstrated with a YLF laser with the wavelength of 1053 nm. The TBGs used in the experiment has the angular selectivity of 1.35mrad, the period of 1.97μm and the diffraction efficiencies of about 92%. Since part of the characteristic spatial frequencies was cleared out with the band-stop angular filter, there was an intensity drop on the edge of the filtered beam. The optical axis for the incident and output beams keeps basically coaxial after filtering, which can be used as a plug-and-play device in the high-power laser systems. The characteristic spatial frequency of 1.98mm-1 corresponds to the TBG deviation angle of 1.35mrad, and the spatial frequencies around the characteristic frequency of 1.98mm-1 were reduced to 20% compared to that of the original beam. The desired bands in the laser beam can be filtered with different TBGs, which has potential applications in high power lasers.

Paper Details

Date Published: 21 April 2017
PDF: 1 pages
Proc. SPIE 10085, Components and Packaging for Laser Systems III, 100850X (21 April 2017); doi: 10.1117/12.2251434
Show Author Affiliations
Xiao Yuan, Soochow Univ. (China)
Xiang Zhang, Soochow Univ. (China)
Fan Gao, Soochow Univ. (China)

Published in SPIE Proceedings Vol. 10085:
Components and Packaging for Laser Systems III
Alexei L. Glebov; Paul O. Leisher, Editor(s)

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