Fluence scan: an unexplored property of a laser beam

Chalupsky, J., Burian, T., Hajkova, J., Juha, L., Polcar, T., Gaudin, J., Nagasono, M., Sobierajski, R., Yabashi, M. and Krzywinski, J. (2013) Fluence scan: an unexplored property of a laser beam. Optics Express, 21 (22), 26363-26375. (doi:10.1364/OE.21.026363).

Abstract

We present an extended theoretical background of so-called fluence scan (f-scan or F-scan) method which is frequently being used for offline focused short-wavelength (XUV, soft X-ray, and hard X-ray) laser beam characterization (Chalupský et al. 2010 Opt. Express 18 27836). The method exploits ablative imprints in various solids to visualize iso-fluence beam contours at different fluence and/or clip levels. By varying the pulse energy, an f-scan curve (clip level as a function of the contour area) can be generated for a general non-Gaussian beam. The fluence scan method greatly facilitates transverse characterization of focused non-Gaussian beams and provides important information about energy distribution within the beam profile. Here we for the first time discuss fundamental properties of the f-scan function and its inverse counterpart (if-scan or iF-scan). Furthermore, we extensively elucidate how it is related to the effective beam area, energy distribution, and to the so called Liu’s plot (Liu 1982 Opt. Lett. 7 196). A new method of effective area evaluation based on weighted inverse f-scan fit is introduced and applied to real data obtained at the SCSS (Spring-8 Compact SASE Source) facility.

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Contributors

Author: T. Polcar

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