Fast and sensitive time-multiplexed gas sensing of multiple lines using a miniature telecom diode laser between 1529 nm and 1565 nm

• High-sensitive multi-species detection around 1550 nm using a modulated grating Y-branch, MG-Y, diode laser tunable between 1529 nm and 1565 nm is presented. The MG-Y diode laser is based on the Vernier effect of two modulated gratings, and exhibits quasi-continuous tuning over 36 nm. Multi-species detection is achieved by fast sequential scanning of single absorption lines of CH4, CO, C2H2, and CO2 distributed over the tuning range of the diode laser. The laser wavelength is scanned about 10 GHz around each absorption line for 5 ms and this is followed by a discrete large jump in operating wavelength to the next line. The MG-Y diode laser has a good repeatability in output frequency between sequential scan segments (< 10 MHz) enabling averaging of the scans. The setup employs digital wavelength modulation spectroscopy, dWMS, with Fourier-based WMS retrieval, applicable through the use of data acquisition cards and coherent sampling. Absorbance sensitivity using 2f-WMS signals of 7x10(-7) in 30 s (all precisions in this paper are at the 1 sigma level) is demonstrated for sensing of four gases and 2x10(-7) when only one gas is detected. Corresponding numbers for 0.5 s of averaging are 4x10(-6) and 1x10(-6).

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TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Annan maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Other Mechanical Engineering (hsv//eng)

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