A study of trace gas detection based on cavity enhanced absorption spectroscopy (CEAS) for power transformer diagnosis

Someya, Ryuta; Imamura, Takeshi; Kanazawa, Yukio; Hatano, Hiroshi; Takahashi, Hazime; Tei, Kazuyoku; Yamaguchi, Shigeru

doi:10.1109/cleopr.2013.6600341

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“…We have even exploited commercially avail-able instruments at our facility to develop a passively locked external cavity (PLEC) system for trace gas sensing. [30][31][32][33][34] This system has a very unique resonant mechanism with an antireflection-coated diode laser (AR-DL) as a light source in combination with a pair of highly reflective mirrors. The resonant frequencies are selected according to the cavity distance, and the resonant light is turned back and injected into the DL active layer (optical feedback).…”

Section: Introductionmentioning

confidence: 99%

Performance characteristics of a passively locked cavity-enhanced absorption spectrometer with wideband-tunable multimode near-infrared light source

Someya

Imamura

Okamoto

et al. 2016

Jpn. J. Appl. Phys.

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A trace material detection system was developed on the basis of cavity-enhanced absorption spectroscopy (CEAS) using a fiber-coupled passively locked external cavity diode laser (PLEC-DL) in the near-infrared (NIR) wavelength region. The oscillation range of an antireflection-coated diode laser (AR-DL) coupled into an external cavity could be simply selected with a narrowband bandpass filter (1 nm), resulting in a stable wavelength oscillation in the wideband tunability between 1640 and 1680 nm. The external cavity acts as a trace material sensor that exhibits excellent flexibility because it is free from the DL source and is carefully designed with mirrors having reflectivities of ca. 99.995 and 99.99%. Trace-level detection was successfully demonstrated with the developed sensor having a minimum detectable absorption coefficient of 2.4 × 10−8 cm−1, which corresponds to 0.15 ppm for CH4 concentration without interference from H2O absorption lines under atmospheric pressure.

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