Model-Based Optimization of Laser Excitation and Detection Improves Spectral Contrast in Noninvasive Diffuse Raman Spectroscopy

Dooley, Max Jordan; Paterson, Thomas; Dexter, Louise; Matousek, Pavel; Dehghani, Hamid; Notingher, Ioan

Abstract

Spatially offset Raman spectroscopy (SORS) is a powerful technique for subsurface molecular analysis of optically turbid samples. Numerical modeling of light propagation has been used to investigate opportunities for improving spectral contrast and signal to noise ratio when imaging regions of interest located 0–4.5mm below the surface in polymer bulk material. Two- and three-dimensional modeling results demonstrate that when analyzing a certain region of interest (ROI) of finite lateral dimensions below the sample surface, offsetting both the laser source and detector in opposite directions from the central point of the ROI can increase the spectral contrast as compared to conventional SORS approach where the detector or the laser source is maintained at the central point (centered SORS). The outlined modeling results have been validated experimentally using a bulk polymer sample with a trans-stilbene ROI (cylinder) below the sample surface. The results show that modeling of the spatial configurations of laser excitation and detection points can be used to optimize the instrument configuration to achieve significant improvements (up to 2.25-fold) in performance over the conventional centered SORS. Such optimal solutions can then be implemented, for example, using robust fiber optic probes, moveable optics, or flexible spatial light modulator instruments for specific applications.

Citation

Dooley, M. J., Paterson, T., Dexter, L., Matousek, P., Dehghani, H., & Notingher, I. (2022). Model-Based Optimization of Laser Excitation and Detection Improves Spectral Contrast in Noninvasive Diffuse Raman Spectroscopy. Applied Spectroscopy, 76(7), 801-811. https://doi.org/10.1177/00037028211072900

• Journal Article Type: Article
• Acceptance Date: Jan 26, 2022
• Online Publication Date: Jan 26, 2022
• Publication Date: 2022-07
• Deposit Date: Feb 18, 2022
• Publicly Available Date: Feb 18, 2022
• Journal: Applied Spectroscopy
• Print ISSN: 0003-7028
• Electronic ISSN: 1943-3530
• Publisher: SAGE Publications
• Peer Reviewed: Peer Reviewed
• Volume: 76
• Issue: 7
• Pages: 801-811
• DOI: https://doi.org/10.1177/00037028211072900
• Keywords: Spectroscopy; Instrumentation
• Public URL: https://nottingham-repository.worktribe.com/output/7353625
• Publisher URL: https://journals.sagepub.com/doi/10.1177/00037028211072900
• Additional Information: Max Jordan Dooley, Thomas Paterson, Louise Dexter, Pavel Matousek, Hamid Dehghani, Ioan Notingher, Applied Spectroscopy. Copyright © 2022. DOI: https://doi.org/10.1177%2F00037028211072900.