From ultrafast holography to ultrafast tomography.

Hörmann M., Cerullo G., Camargo F.V.A., van Hulst N., Liebel M.
  Martedì 13/09   09:00 - 13:30   Aula L - Christa Mc Auliffe   VI - Fisica applicata, acceleratori e beni culturali   Presentazione
In optical diffraction tomography (ODT) the real three-dimensional structure of even dense objects is retrieved by combining microscopic amplitude and phase images from different angles. A common scheme to perform this angle-scanning utilizes off-axis holography, in which a reference wave is interfered with the wave front induced by the object. However, the interference relies on monochromatic light sources with long coherent lengths. Here, we present a setup capable of performing ODT with femtosecond pulses and a bandwidth of over $100 {nm}$, respectively, in an off-axis scheme. To maintain the interference the wave fronts are perfectly matched spatially and spectrally. Further, we perform test measurements on how the chirp introduced by dispersive media influences the interference quality depending on the bandwidth. The results of this study show the successful implementation and allow directly to either perform ODT with spectral information or to extend tomography to the realm of ultrafast transient processes in pump-probe experiments, which can find application in material science ($e.g.$, photoinduced charge carrier diffusion) or bio-physics (tracking gold nanoparticles in cells).