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Implementation of a turret-mounted optical assembly for femtosecond laser Bessel-beam shaping for machining applications
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Paper Abstract

Femtosecond (fs) laser beams may be shaped into Bessel beam (BB) profiles by spatial light modulators or axicon lenses. Temporally reshaping laser pulses by chirping and stretching further alters the spatio-temporal intensity pattern within the elongated focal volume. Such beam shaping applied to high-power pulses is useful for numerous materials processing applications, enabling fabrication of very high aspect ratio columns in optically transparent materials. We report the development of a compact, adaptable microscope turret-mounted assembly containing an axicon and a high numeric aperture aspheric lens imaging system, and the use of temporal reshaping studies in various fs laser machining applications. Depending on axicon angle, lens separations, and the refractive index of the substrate, the central lobe diameter of the BB may be less than 1 μm but extending over 500 μm long, effectively forming a narrow, long cylindrical column. Moreover, because an entire column can be machined with a single, energetic pulse, high processing rates are possible. Materials such as fused silica and polymers are found to be good candidates for directly formed voids. Microchannels in silica can be used in single-molecule recycling experiments, while permeable membranes in thin plastics are sought for cellular studies, passing nutrients but not cells. In rigid crystalline structures like diamond and sapphire, the substrate material is transformed in place. In particular, a BB column machined through electrically insulating diamond can become conductive graphite, which is of interest for developing radiation-hard detectors of highenergy particles.

Paper Details

Date Published: 9 September 2019
PDF: 11 pages
Proc. SPIE 11107, Laser Beam Shaping XIX, 111070A (9 September 2019); doi: 10.1117/12.2529420
Show Author Affiliations
Brian K. Canfield, The Univ. of Tennessee Space Institute (United States)
Alexander Terekhov, The Univ. of Tennessee Space Institute (United States)
Lino Costa, The Univ. of Tennessee Space Institute (United States)
Lloyd M. Davis, The Univ. of Tennessee Space Institute (United States)
The Univ. of Tennessee Knoxville (United States)


Published in SPIE Proceedings Vol. 11107:
Laser Beam Shaping XIX
Angela Dudley; Alexander V. Laskin, Editor(s)

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