Abstract
This paper presents a complete, compact, and low power consumption instrument designed for time-domain near-infrared spectroscopy. It employs two custom-designed pulsed diode lasers (operating at 830 and 670 nm, with average optical power higher than 2 mW at 40 MHz repetition frequency), a single-photon detection module (based on a 1 mm2 active area silicon photomultiplier), and a custom time-to-digital converter with 10 ps time resolution. The system experimental characterization shows an instrument response function narrower than 300 ps (full-width at half maximum), with measurement stability better than ±1% over several hours of operation. The instrument, which is housed into a compact aluminum case (size 200 × 160 × 50 mm3), is specifically tailored for portability and ease of operation, hence fostering the diffusion of time-domain diffuse optics techniques. Thanks to a total power consumption lower than 10 W, this system is suitable for battery operation, thus enabling on-field measurements.
Highlights
Over the past few decades, the interest in non-invasive optical monitoring techniques is growing in several fields as powerful tools for probing different properties of a medium [1]–[3]
Following sections focus on the design of main building blocks of the system, namely, i) the two pulsed diode lasers, ii) the single-photon detection module and iii) the time-measurement and control systems
It is possible to implement a form of Differential Non-Linearity (DNL) correction, by dividing the acquired Time-Correlated Single-Photon Counting (TCSPC) curves by a reference waveform, which represents the shape of non-linearity over the measurement range
Summary
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