A new gas detection technique utilizing amplified spontaneous emission light source from a Tm⁺³/Ho⁺³ co-doped silica fibre in the 2.0 μm region

A new technique for the measurement of the concentration of gas species is presented. The method is based on absorption spectroscopy in the infrared region utilizing a high-power broad band amplified spontaneous emission source from an optical fibre. Vibrational bands of CO₂ gas in the range 1.9-2.1 μm were measured and the relative intensities of bands were calibrated in terms of concentration. The amplified spontaneous emission from a Tm⁺³/Ho⁺³ co-doped silica fibre pumped near 800 nm was used as a light source that consisted of the ³H₄ → ³H₆ transition of the Tm⁺³ ion and the ⁵I₇ → ⁵I₈ transition of the Ho⁺³ ion with a full width at half maximum of 225 nm and total output power over 1 mW. The technique has potential for the simultaneous detection of multiple gas species due to its high spectral energy density over a wide wavelength band in the infrared where the vibrational overtones of gas molecules are located.