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Proceedings Paper

A new method of determination of ablation threshold contour in the spot of focused XUV laser beam of nanosecond duration
Author(s): Karel Kolacek; Jiri Schmidt; Jaroslav Straus; Oleksandr Frolov; Václav Prukner; Radek Melich; Andrei Choukourov
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Paper Abstract

It is well known that at interaction of femtosecond Extreme Ultraviolet Radiation (XUV) with a surface it is possible – according to local fluency - to distinguish two main regions: the desorption region (when efficiency η of removing particles is <10%), and the ablation region (when efficiency η ~ 100%). In this case, the ablation threshold determination is very simple and relatively accurate. It was e.g. shown that with the help of mapping of morphology of the ablationdug- craters it is possible to determine the fluency distribution in/near the beam focus. However, recently we found that (1) the desorption efficiency η for nanosecond pulses is much higher than that for femtosecond ones and spans from zero at the periphery imprint to ~90% at the ablation threshold; this complicates the ablation threshold determination; (2) the direct nano-structuring of solid surfaces is possible only in the desorption region (e.g. the diffraction pattern generated in windows of in-proximity-standing-grid [K.Kolacek et.al., Laser and Particle Beams 30, 57-63, (2012)] is visible only in these parts of laser-beam-spot, which correspond to the desorption region). This prompted us to use this nano-patterning for determination of ablation threshold contour. The best possibility seems to be covering the laser beam spot by interference pattern. For that, it was necessary to develop a new type of interferometer, which (a) provides as dense interference pattern as possible, (b) uses practically all the energy of laser beam, (c) works with focused beams. Such interferometer has been designed and is described in this contribution.

Paper Details

Date Published: 3 May 2013
PDF: 9 pages
Proc. SPIE 8777, Damage to VUV, EUV, and X-ray Optics IV; and EUV and X-ray Optics: Synergy between Laboratory and Space III, 87770N (3 May 2013); doi: 10.1117/12.2020261
Show Author Affiliations
Karel Kolacek, Institute of Plasma Physics of the ASCR, v.v.i. (Czech Republic)
Jiri Schmidt, Institute of Plasma Physics of the ASCR, v.v.i. (Czech Republic)
Jaroslav Straus, Institute of Plasma Physics of the ASCR, v.v.i. (Czech Republic)
Oleksandr Frolov, Institute of Plasma Physics of the ASCR, v.v.i. (Czech Republic)
Václav Prukner, Institute of Plasma Physics of the ASCR, v.v.i. (Czech Republic)
Radek Melich, Institute of Plasma Physics of the ASCR, v.v.i. (Czech Republic)
Andrei Choukourov, Charles Univ. in Prague (Czech Republic)


Published in SPIE Proceedings Vol. 8777:
Damage to VUV, EUV, and X-ray Optics IV; and EUV and X-ray Optics: Synergy between Laboratory and Space III
Libor Juha; René Hudec; Ladislav Pina; Saša Bajt; Richard London, Editor(s)

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