Thin-film waveguide technology towards mid-infrared lab-on-chip systems
Auch gedruckt in der BibliothekW: W-H 15.096
FakultätFakultät für Naturwissenschaften
InstitutionInstitut für Analytische und Bioanalytische Chemie
Institut für Oberflächenchemie und Katalyse
Ressourcen- / MedientypDissertation, Text
Datum der Erstveröffentlichung2017-05-12
This cumulative thesis focuses on the development of thin-film waveguide technologies and their application for chem/bio sensors in food and feed quality monitoring scenarios. The thesis is based on seven peer-reviewed journal articles, which were published in collaboration with several research groups and industrial partners. The research presented in this thesis covers individual development steps towards mid-infrared (MIR) lab-on-chip systems based on thin-film waveguides and quantum cascade laser technology. Firstly, an extensive study on the modal behavior of GaAs/AlGaAs thin-film waveguides was performed. A simulation protocol was established for maximizing the sensitivity of such waveguide systems with main emphasis on their combination with broadly tunable quantum cascade lasers (QCL). Based on these design studies, optimized frequency-matched (i.e., matched to the respective analyte MIR signatures) waveguide structures and geometries may be derived for fabricating highly sensitive transducers applied in MIR chem/bio sensors and lab-on-chip systems. Consequently, the first functional monolithically integrated mid-infrared Mach-Zehnder interferometer was demonstrated based on the GaAs/AlGaAs semiconductor waveguide system. In a second step a modular waveguide assembly was designed and fabricated providing an easy-to-handle device despite micrometer-sized waveguide dimensions. This device was pivotal towards establishing advanced QCL-based analytical devices facilitating handling and alignment of thin-film waveguides, which to date was a limiting factor for the application of such miniaturized MIR sensing systems in real-world scenarios. Finally, the combination of various QCL light sources with the developed on-chip waveguide assemblies comprising frequency-matched thin-film waveguides paved the way towards miniaturized MIR sensors and more elaborate lab-on-chip systems. The potential of waveguide-and laser-based MIR analyzers as a viable alternative to commonly used Fourier transform infrared spectroscopy (FTIR) was demonstrated for several analytical scenarios. Last but not least, a new approach for spectroscopic mycotoxin analysis at EU regulatory limits utilizing the developed MIR sensor was developed, prototyped, and tested (MYCOSPEC). Thereby, an extraction and analysis procedure was established for a variety of agricultural commodities including wheat, maize and peanuts, which enabled rapid and potentially on-site classification of mycotoxin contaminated and uncontaminated samples at the respective limits demanded by EU regulations, thereby providing an innovative technology for food and feed importers and manufacturers. In summary, the developed MIR sensing technologies may readily evolve into MIR lab-on-chip systems facilitating rapidly responding and on-site applicable analytical platforms for screening and monitoring in a wide range of analytical application scenarios.