Non-linear optical processes such as coherent anti-Stokes Raman scattering and sum frequency generation offer a view into the chemical and biological interactions of molecules that is distinctly different from linear techniques like near infra-red and fluorescence. This insight comes at a cost: non-linear techniques are more sensitive to external perturbations of the system, increasing the noise and decreasing the repeatability of the data. We work here on both aspects of these non-linear techniques, taking advantage of their power to offer new imaging techniques as well as working to quantify and reduce the non-resonant noise inherent to the system. In pursuit of the first part, we look at formalin fixed paraffin embedded tissue samples. This is the most common form of tissue storage in the world. However, the paraffin renders them unavailable for spectroscopic study. We introduce a new technique, combination coherent anti-Stokes Raman scattering microscopy and sum frequency generation microscopy, to avoid the issue of paraffin signal contamination. This high resolution, widefield technique allows for the separate identification of paraffin and the tissue embedded within it. We show in this work the capability of this technique to enable high throughput automated detection of osteoporosis in mice. In pursuit of the second part, we demonstrate experimentally for the first time, deferred build up in coherent anti-Stokes Raman scattering. We show that coherent anti-Stokes Raman scattering signal is maximized when the probe pulse is delayed by an amount dependent on the probe width and the material itself. Non-resonant contamination, however, is maximized when the probe delay is zero, meaning that it is possible to decrease the non-resonant noise while increasing the desired signal. We also show that the dephasing time is inversely dependent on the probe width, so narrower probe pulses allow for further delayed probe pulses, which in turn decrease non-resonant noise more. We demonstrate this technique by looking at the effects of hydrogen bonding in pyridine-water complexes.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-7038 |
| Date | 08 December 2023 |
| Creators | Semon, Bryan |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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