Regensburg 2019 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 12: Poster II

BP 12.19: Poster

Dienstag, 2. April 2019, 14:00–16:00, Poster B2

Analysis of Organic Molecules in the THz Regime using Whispering-Gallery Mode Resonators — •Felix Lammermann, Maria Th. Schlecht, Stefan Malzer, and Heiko B. Weber — Lehrstuhl für Angewandte Physik, FAU Erlangen-Nürnberg, Germany

Distinguishing small amounts of organic or biomolecules like single- and double-stranded DNA in aqueous solutions in a fast and non-destructive way is of great interest for bioanalysis [1]. For this task, we present a measurement scheme based on whispering-gallery mode resonators (WGMR) and continous-wave THz-radiation in the frequency range from 80 GHz to >1 THz. The evanescent field of a PTFE THz-waveguide couples to a WGMR made of PE (disk  10 mm). A hole in this disk allows to insert a cannula filled with the fluid to be examined.
This local disturbance of the refractive index of the disk severely shifts the resonance frequencies of the WGMR such that the organic molecules can be identified. In a first step, the frequency shifts of short-chained alcohols and organic materials with a high refractive index like glycerine were investigated. We were able to distinguish 1- and 2-propanol which only differ by the position of the −OH group. We verified our results with finite element method simulations. To differentiate various sucrose concentrations of aqueous solutions the sensitivity of our setup had to be improved. Thus, the transmission through larger volumes of the corresponding fluid was measured to determine its specific absorption frequencies. Studying the resonance shifts of the resonator close to those should severely increase our selectivity.
[1] Weisenstein, DOI: 10.1109/IRMMW-THz.2018.8510052 (2018)