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Disputation Mohamed Mahmoud Essam Ghobara

Feb 10, 2025 | 04:00 PM
Thema der Dissertation:
Optics of Diatom Frustules Toward Applications and Photobiology
Abstract: Diatoms are an outstanding group of unicellular microalgae that can be found in almost all aquatic ecosystems, playing critical roles in the global carbon fixation and oxygen cycle. The cell wall surrounding diatom living cells, named frustule, is synthesized from amorphous hydrated silica with outstanding properties and plenty of geometries and ultrastructures varying between different species. The frustule consists of subcomponents; valves and girdle bands, held together in the living state but can be extracted and retrieved after death. The retrieved valves/girdle bands exhibit an outstanding ultrastructure, including the presence of nano-/micro-pores arrays resembling the artificial photonic crystal slabs and diffraction gratings. That is why the optical properties and light modulation capabilities of these siliceous parts have recently captured a wide interest and have been suggested for several optical applications as an eco-friendly and cost-effective alternative to artificial structures. Despite the previous efforts to understand the light modulation capabilities of these frustules and their subcomponents, more efforts are still required, and many missing gaps need to be filled. Therefore, this thesis aims to deepen the understanding of their light modulation capabilities, while focusing on their optical near field and Fresnel regime. The results obtained could increase the applicability of diatom valves in optical applications and understand the possible photobiological roles of their frustules. Additionally, the thesis also aims to investigate implementing the extracted clean valves as optical building blocks in photonic and optoelectronic applications, which adds to the previous efforts in the literature.

Time & Location

Feb 10, 2025 | 04:00 PM

Hörsaal A (1.3.14)
Fachbereich Physik, Arnimallee 14, 14195 Berlin