Wavelength-modulation detection of acetylene with a near-infrared external-cavity diode laser

Abstract

An external-cavity diode laser operating at 1500 nm was used to record the combination band of acetylene (C(2)H(2)). By combination of wavelength-modulation spectroscopy with a noise-canceler detection circuit, a minimum detectable absorbance of 4.8 × 10(-4) with a 300-ms time constant was achieved, although this result was limited by étalon fringes. When combined with this detection technique, continuous, widely tunable output from an external-cavity laser is ideally suited for high-resolution absorption spectroscopy with excellent sensitivity.