University of Oulu

J. Kekkonen, T. Talala, J. Nissinen and I. Nissinen, "On the Spectral Quality of Time-Resolved CMOS SPAD-Based Raman Spectroscopy with High Fluorescence Backgrounds," in IEEE Sensors Journal. doi: 10.1109/JSEN.2020.2966119

On the spectral quality of time-resolved CMOS SPAD-based Raman spectroscopy with high fluorescence backgrounds

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Author: Kekkonen, Jere1; Talala, Tuomo1; Nissinen, Jan1;
Organizations: 1Circuits and Systems Research Unit, University of Oulu, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.8 MB)
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Language: English
Published: Institute of Electrical and Electronics Engineers, 2020
Publish Date: 2020-03-02


The fluorescence background in Raman spectroscopy can be effectively suppressed by using pulsed lasers and time-gated detectors. A recent solution to reduce the high complexity and bulkiness of the time-gated systems is to implement the detector by utilizing time-resolved single-photon avalanche diodes (SPADs) fabricated in complementary-metal-oxide-semiconductor (CMOS) technology. In this study, we investigate the effects of fluorescence-to-Raman ratio, recording time and excitation intensity on the quality of Raman spectra measured by using one of the furthest developed fluorescence-suppressed Raman spectrometers based on a time-resolved CMOS SPAD line sensor. The objectives were to provide information on the significance of the different causes behind the distortion of the measured Raman spectra with various measurement conditions and to provide general information on the possibilities to exploit the high-intensity non-stationary pulsed laser excitation to gain additional improvement on the spectral quality due to laser-induced fluorescence saturation. It was shown that the distortion of the spectra with samples having short fluorescence lifetimes (~2 ns) and high fluorescence-to-Raman ratios, i.e. with challenging samples, is dominated by the timing skew of the sensor instead of the shot noise caused by the detected events. In addition, the actual reason for the observed improvement in the spectral quality as a function of excitation intensity was discovered not to be the conventionally thought increased number of detected photons but rather the laser-induced fluorescence saturation. At best, 26% improvement to the signal-to-noise ratio was observed due to fluorescence saturation.

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Series: IEEE sensors journal
ISSN: 1530-437X
ISSN-E: 1558-1748
ISSN-L: 1530-437X
Volume: 20
Issue: 9
Pages: 4635 - 4645
DOI: 10.1109/JSEN.2020.2966119
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: This work was supported by the Academy of Finland under Contract 314404, Contract 323719 and Contract 307362 (Centre of Excellence in Laser Scanning Research.
Academy of Finland Grant Number: 314404
Detailed Information: 314404 (Academy of Finland Funding decision)
323719 (Academy of Finland Funding decision)
307362 (Academy of Finland Funding decision)
Copyright information: © The Authors 2020. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see