Dresden 2017 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 7: Poster: Microanalysis and Microscopy

MI 7.13: Poster

Mittwoch, 22. März 2017, 18:00–20:00, P4

Investigation of biological structures from fossils and simulation of their optical properties — •Ran Zhang, Enrico Langer, Barbara Adolphi, Andreas Voigt, and Andreas Richter — Technische Universität Dresden, Institut für Halbleiter- und Mikrosysteme

Diffraction gratings and photonic crystals play an important role for smart technical applications. The investigation of photonic structures in biology is an interesting scientific endeavor, because it can contribute to a better biological classification and since it may trigger bio-inspired technological developments. In this work, fossil surfaces from crustaceans were investigated by means of both scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) in the low-vacuum mode. On the 150 million years old crayfishes "Eryma modestiformis" and "Palaeastacus fuciformis" we discovered structures with different dielectric constants and similar width (about 200 nm) that are arranged periodically on the surface. Moreover, the investigation by EDS allows to draw conclusions on the composition of the original fossil materials. The detected periodic structures can be regarded as 1D and 2D diffraction gratings. Electromagnetic waves would be reflected depending on the wavelength in different directions. We show calculations of these angles by diffraction equations and the reflection of visible light with various colors. Another unusual structure with a finer and more regular arrangement was observed, which was unveiled as a diatom. It can be treated as a photonic crystal slab. With the measured geometric data and material composition, a biological monoclinic photonic crystal model was built. The photonic bands of this structure (which allows conclusions about the reflectance behavior in the horizontal direction) were calculated by the plane wave expansion method [1]. Future work will include the application of the finite difference time-domain method and rigorous coupled wave analysis in order to calculate the transmission and reflection spectra for arbitrary angles of incidence.

[1] S.G. Johnson and J. D. Joannopoulos, Optics Express 8, (2001) 173-190.