Performance of a 16×256 time-resolved CMOS single-photon avalanche diode line sensor in Raman spectroscopy applications

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Remote defence: https://oulu.zoom.us/j/66631323183?pwd=WnA0RUVrcG9mNzd5bmUxT3QxQmQvUT09

Topic of the dissertation

Performance of a 16×256 time-resolved CMOS single-photon avalanche diode line sensor in Raman spectroscopy applications

Doctoral candidate

Master of Health Sciences Jere Kekkonen

Faculty and unit

University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Circuits and Systems Research Unit

Subject of study

Electrical Engineering

Opponent

Professor Mika Pettersson, University of Jyväskylä

Custos

Associate Professor Ilkka Nissinen, University of Oulu

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Performance of a modern sensor capable of time stamping single light particles in Raman spectroscopy applications

Raman spectroscopy is a powerful optical tool that utilizes Raman-scattering, which is one of the light-matter interaction mechanisms, to resolve the chemical composition of different kinds of samples. The main challenge of Raman spectroscopy has been the laser-induced fluorescence background of some samples that can mask the actual Raman signal. One effective method to suppress the fluorescence background is to discriminate the Raman signal from the fluorescence background in the time-domain. In order to do this, sensors that are capable of very precisely (with resolution better than one billionth of a second) stamp the arrival times of the light particles from the sample are needed.

In this work was studied the performance of a modern sensor capable of precisely time stamping the arrival times of single light particles in Raman spectroscopy applications. First was studied the effects of various parameters on the quality of the spectra recorded with the studied Raman-spectrometer. It was shown that the dominating noise source with highly fluorescent samples is actually the distortion of the spectra caused by the timing skew of the sensor instead of the traditionally thought shot noise.

This work also showed that the studied Raman spectrometer can be used to form chemical images of samples that are traditionally thought to be demanding samples for Raman spectroscopy due to their high fluorescence background. The chemical imaging was demonstrated in two different applications. In the first application was mapped the distribution of minerals carrying rear earth elements in a rock sample that was drilled from a deposit located in Southern Sweden. In the second application was shown that by Raman imaging extracted human teeth the different tooth tissue types and even initial caries can be recognized from the teeth based on the recorded Raman signatures. It was also shown that the quality of the spectra measured with the studied spectrometer was higher compared to the quality of the spectra measured with a commercial Raman spectrometer that is incapable of stamping the arrival times of the light particles.

Furthermore, this work demonstrated that the studied sensor can be also utilized in more specialized Raman radar and Raman depth-profiling applications. In Raman radar operation, the studied spectrometer can define both the chemical composition and distance of a target meters away with a centimeter-scale resolution based on the recorded time-stamped Raman signal. In Raman depth-profiling, the depth resolution of the studied spectrometer was measured to be in the scale of millimeters. Raman depth-profiling was also performed with a more novel data acquisition method that significantly increases the speed of the depth-profiling. Both Raman radaring and Raman depth-profiling has many potential applications, for example, in industrial process monitoring.
Last updated: 25.3.2021