Diode laser-based photoacoustic spectroscopy with interferometrically-enhanced cantilever detection

A novel sensitive approach to detect weak pressure variations has been applied to tunable diode laser-based photoacoustic spectroscopy. The sensing device consists of a miniature silicon cantilever, the deflection of which is detected with a compact Michelson-type interferometer. The photoacoustic system has been applied to the detection of carbon dioxide (CO2) at 1572 nm with a distributed feedback diode laser. A noise equivalent sensitivity of 2.8 x 10-10 cm-1WHz-1/2 was demonstrated. Potential improvements of the technique are discussed.