title: Wavelength modulation waveforms in laser photoacoustic spectroscopy.
abstract: Different wavelength modulation waveforms were studied comprehensively in tunable diode laser photoacoustic spectroscopy. The generation of the photoacoustic signal was studied by way of simulations and experiments. A cantilever-enhanced photoacoustic detector and CO(2) sample gas were used in the experiments. The modulation waveforms compared in this study were sinusoidal, triangular, shaped, and quasi-square waves. All four waveforms allow background-free detection of trace gases. Compared to the conventionally used sinusoidal modulation, the triangular, shaped, and quasi-square waves enhanced the photoacoustic signal by factors of 1.12, 1.42, and 1.57, respectively.
authors.affiliation: Optics Laboratory, Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland. jaakko.saarela@tut.fi
authors.forename: Jaakko
authors.initials: J
authors.lastname: Saarela
authors.forename: Juha
authors.initials: J
authors.lastname: Toivonen
authors.forename: Albert
authors.initials: A
authors.lastname: Manninen
authors.forename: Tapio
authors.initials: T
authors.lastname: Sorvajärvi
authors.forename: Rolf
authors.initials: R
authors.lastname: Hernberg