title: Remote mid-infrared photoacoustic spectroscopy with a quantum cascade laser.
abstract: We demonstrate non-contact remote photoacoustic spectroscopy in the mid-infrared region. A room-temperature-operated pulsed external-cavity quantum cascade laser is used to excite photoacoustic waves within a semitransparent sample. The ultrasonic waves are detected remotely on the opposite side of the sample using a fiber-optic Mach-Zehnder interferometer, thereby avoiding problems associated with acoustic attenuation in air. We present the theoretical background of the proposed technique and demonstrate measurements on a thin polystyrene film. The obtained absorption spectrum in the region of 1030-1230  cm(-1) is compared to a spectrum obtained by attenuated total reflection, showing reasonable agreement.
authors.forename: Thomas
authors.initials: T
authors.lastname: Berer
authors.forename: Markus
authors.initials: M
authors.lastname: Brandstetter
authors.forename: Armin
authors.initials: A
authors.lastname: Hochreiner
authors.forename: Gregor
authors.initials: G
authors.lastname: Langer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Märzinger
authors.forename: Peter
authors.initials: P
authors.lastname: Burgholzer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lendl