Chirp control of femtosecond-pulse scattering from drag-reducing surface-relief gratings

Autor(en): Eggert, Juliane
Bourdon, Bjoern
Nolte, Stefan
Rischmueller, Joerg
Imlau, Mirco 
Stichwörter: Optics; REDUCTION
Erscheinungsdatum: 2018
Volumen: 6
Ausgabe: 6
Startseite: 542
Seitenende: 548
The role of chirp on the light-matter interaction of femto- and pico-second laser pulses with functional structured surfaces is studied using drag-reducing riblets as an example. The three-dimensional, periodic microstructure naturally gives rise to a mutual interplay of (i) reflection, (ii) scattering, and (iii) diffraction phenomena of incident coherent light. Furthermore, for femtosecond pulses, the structure induces (iv) an optical delay equivalent to a consecutive temporal delay of 230 fs in places of the pulse. These features enable studying experimentally and numerically the effect of tuning both pulse duration tau and spectral bandwidth Delta omega on the features of the wide-angle scattering pattern from the riblet structure. As a result, we discovered a significant breakdown of fringes in the scattering pattern with decreasing pulse duration and/or increasing spectral bandwidth. This unique type of chirp control is straightforwardly explained and verified by numerical modeling considering the spectral and temporal interaction between different segments within the scattered, linearly chirped pulse and the particular geometric features of the riblet structure. The visibility of the fringe pattern can be precisely adjusted, and the off-state is achieved using tau < 230 fs or Delta omega > 2.85 x 10(13) rad/s.
ISSN: 23279125
DOI: 10.1364/PRJ.6.000542

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