Instruments and Applications for Absorption and Fluorescence Spectroscopy

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Our research group is active in the areas of laser spectroscopy and sensing. We build spectrometers, fiber probes, refractometers, as well as micro-sensors for optical absorption, fluorescence, mechanical strain, vibration and acceleration. Most of the instruments we develop are designed to detect and quantify chemicals outside a chemistry lab, i.e. by non-experts and in environments that may be as hostile as the inside of an engine. With our expertise in chemistry, engineering, and optics we can take full advantage of the advances of the commercial developments in the telecom, imaging and sensing areas. When developing instruments we fabricate prototypes, write our own software and frequently design our own electronic circuitry. In all research programs, we first build in-house expertise and then work with collaborators in industry and academia on further development of our instruments that is then geared towards their applications. This gives our research the largest impact and provides HQP with an opportunity to build an international network of industrial and academic contacts. Here, we propose to build a number of new instruments and develop new techniques that give us and our collaborators much improved tools to quantify chemicals. The project suites fall into four categories spanning instrument design, fundamental optics, spectroscopy, photochemistry and micro-analytical chemistry. Even though we apply spectroscopic methods, the analyte concentrations will not be determined from light intensity measurements. Light intensity is notoriously difficult to quantify in uncontrolled environments and we therefore focus on techniques that let us infer concentrations either from decay rates (ring-down times), modulation phase shifts, interferograms, resonance frequency shifts, or, if everything else fails, intensity ratios. For example, in the next years we will apply new techniques in cavity-enhanced spectroscopy to micro-photonic resonators. We will use micro-sphere resonators and silicon nanowire sensors to achieve an unprecedented level of quantitation of analytes by measuring resonance frequency shifts and optical decay times. We will also take full advantage of our recent co-development of one of the most sensitive and noise-immune fiber strain sensors to develop an optical fiber probe for absorption (!) spectroscopy. To demonstrate its noise-immunity this fiber strain sensor was previously used as a guitar pickup, but it has a much greater potential as a fiber optic hydrophone for photoacoustic spectroscopy. Finally, we will use the latest generation of digital micromirror arrays to perform “binary” Fourier transform spectroscopy using UV-Vis light. This new programmable lightsource will be used to make fluorescence excitation-emission matrix spectroscopy about 1000-times faster as is currently possible – without any loss in spectral resolution. These new tools combined with recent innovations in film characterization measurements will allow us to develop the next generation of chemical micro-sensors. Industrial partners and academic experts, with whom we already collaborate, will work with us in the application of these new systems to environmental monitoring, chemical process control, engine fluid monitoring, and chemical micro-analysis. The students who advance this research will not only obtain invaluable technical expertise in instrument design, material science, optics, and analytical chemistry, but they will also become competent communicators and project managers. Combined with the international exposure that all HQP obtain they are well-positioned to make an impact in, both, industrial R&D as well as in academic research.