Abstract
We developed a real-time spectroscopy system for continuous measurement using a Fourier-domain mode-locked (FDML) laser. The FDML laser was driven at a sweep rate of 50 kHz in the near-infrared region of 1550 nm. To achieve robust real-time measurement, the spectroscopy system properly designs the pulse modulation of the FDML laser and the length of the reference optical path. The intensity fluctuation of the FDML laser was corrected by introducing a reference optical path. We demonstrated that the spectroscopy system performs continuous measurements for 1 min or more with a time resolution of 20 μs.
Highlights
Near-infrared spectroscopy has proven to be a powerful method for nondestructive and noncontact analysis of the state of matter
The Fourier-domain mode-locked (FDML) laser after fiber optical switch (FSW) was measured by extracting the forward scan light using FSW with a pulsewidth tPW of 7 μs
As some of the sweep light is extracted by the FSW with a pulsewidth of tPW = 7 μs, as shown in Fig. 1, the sweep band of the extracted light is reduced below 30 nm
Summary
Near-infrared spectroscopy has proven to be a powerful method for nondestructive and noncontact analysis of the state of matter. Very few studies have reported on real-time spectroscopy systems for continuous high-speed measurements to meet these demands. We developed a real-time spectroscopy system for continuous high-speed measurements with an FDML laser. The spectroscopy system achieves robust continuous measurement by appropriately designing the pulse modulation of the FDML laser and the length of the reference optical path. Mance et al reported transient absorption spectral measurements of acetylene–oxygen gas mixture undergoing combustion [15]. They estimated postreaction temperature and pressure from the spectra of hydroxyl (OH) radical in the 1550-nm region. In this letter, we used the FDML laser with a high sweep rate of 50 kHz in the near-infrared region of 1550 nm. The experiment measured continuous changes in the spectrum for a measurement time of 60 s with a time resolution of 20 μs
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