Straight and linearly tapered capillaries produced by femtosecond laser micromachining

Wiggins, Mark and Reijnders, M. P. and Abu-Azoum, Salima Saleh and Hart, Kerri and Vieux, Gregory and Welsh, Gregor H. and Issac, Riju and Yang, Xue and Jones, David and Jaroszynski, Dino (2012) Straight and linearly tapered capillaries produced by femtosecond laser micromachining. Journal of Plasma Physics, 78 (specia). pp. 355-361. ISSN 0022-3778 (https://doi.org/10.1017/S0022377812000062)

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Abstract

Gas-filled capillary discharge waveguides are a commonly employed medium in laser–plasma interaction applications, such as the laser wakefield accelerator, because they can simultaneously guide high-power laser pulses while acting as the medium for acceleration. In this paper, the production of both straight and linearly tapered capillaries using a femtosecond laser micromachining technique is presented. A tapered capillary is shown to possess a smooth variation in diameter (from 305 μm to 183 μm) along its entire 40 mm length, which would lead to a longitudinal plasma density gradient, thereby dramatically improving the laser–plasma interaction efficiency in applications. Efficient guiding with up to 82% energy transmission of the fundamental Gaussian mode of a low intensity, 50 fs duration laser pulse is shown for both types of capillary waveguide.