Laser diode photoacoustic and FTIR laser spectroscopy of formaldehyde in the 2.3 μm and 3.5 μm spectral range

The room temperature operating GaInAsSb/AlGaAsSb based diode laser and 66 K InAsSb/InAsSbP laser diode both operating in spectral range of formaldehyde absorption 4350-4361 cm−1 and 2821-2823 cm−1 have been characterized and compared. Very precise arrangement of laser absorption together with high resolution Fourier transform technique was tested. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) diluted by nitrogen for the strongest absorption line of the ν3 + ν5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm−1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of ν1, ν5).