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Compact optical probe for time-resolved NIRS-imaging

: Saha, Sreenil; Lu, Yuankang; Weyers, Sascha; Lesage, Frederic; Sawan, Mohamad


IEEE Sensors Journal 20 (2020), Nr.11, S.6101-6113
ISSN: 1530-437X
ISSN: 1558-1748
Fraunhofer IMS ()
time-gated (TG) detector; vertical cavity surface emitting laser (VCSEL); single-photon avalanche diode (SPAD); near-infrared spectroscopy (NIRS)

We present the design of a standalone optical probe integrated with a Time-Gated Single Photon Detection module and Pulsed Light Emission unit. The detection module is capable of detecting photons in specific time windows, thus enabling the measurement of very faint optical signals. The pulse repetition frequency extends up to 100 MHz with a gate-ON time range up to 35ns. The module is user-configurable via a PC interface and can be integrated in any optical setup. The pulsed light emission unit uses a 50 GHz GaAs Vertical Cavity Surface Emitting Laser diode. Experimental characterization was conducted for all the building blocks of the module to ensure its proper functioning. The module was also employed in a real-life application, heart rate monitoring by illuminating the index finger of a volunteer. The novelty of the proposed miniaturized optode lies in the development of a simplified interface for portable Brain-computer interfaces which can be effectively used in applications such as Near-Infrared Spectroscopy and functional brain imaging.