Photonics Research, 2018, 6 (6): 06000542, Published Online: Jul. 2, 2018
Chirp control of femtosecond-pulse scattering from drag-reducing surface-relief gratings Download: 676次
Optical inspection Surface measurements, figure Linear and nonlinear light scattering from surfac Optical sensing and sensors Chirping Femtosecond phenomena
Abstract
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 τ and spectral bandwidth Δ ω 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 τ < 230 fs or Δ ω > 2.85 × 10 13 rad / s .
Juliane Eggert, Bjoern Bourdon, Stefan Nolte, Joerg Rischmueller, Mirco Imlau. Chirp control of femtosecond-pulse scattering from drag-reducing surface-relief gratings[J]. Photonics Research, 2018, 6(6): 06000542.