Berlin 2001 – scientific programme
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Q: Quantenoptik
Q 30: Poster: Laser in Medicine
Q 30.6: Poster
Friday, April 6, 2001, 12:30–15:00, AT2
A cw-OPO based photoacoustic trace gas detector — •Alexander Popp1, Frank Müller1, Stephan Schiller2, and Frank Kühnemann1 — 1Institut für Angewandte Physik, Wegelerstr. 8, 53115 Bonn — 2Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf
Our cw-OPO based photoacoustic spectrometer is designed to detect trace
gas amounts of biogenic volatiles such as methane, ethane, ethylene,
acetaldehyde and isoprene. Their C-H stretching modes are situated in the
frequency range of 2800-3200 cm−1.
In this mid-infrared region the freely tunable OPO replaces the line
tunable
CO-overtone laser. By tuning the OPO to the maximum absorption frequency or
other distinct features of the molecular spectra sensitivity and
selectivity
of the detection are improved.[1]
The continuous wave, pump enhanced,
single
resonant OPO [2] is pumped at 1064 nm by a 3 W Nd:YAG-laser. It delivers
more
than 100 mW of idler power between 3.1 and 3.5 µ m. By splitting up the
OPO cavity into a pump-enhancement-cavity and a signal-resonant-cavity the
continuous tuning range of 500 MHz can be increased to a few GHz.[3]
The chopped idler beam is focussed into the resonant photoacoustic cell,
which has
a passivated inner surface and low volume to ensure a rapid gas exchange
and
less memory effects caused by polar molecules.
Funded by the DFG: KU 1245/2-1
[1] F. Kühnemann, et. al., Appl. Phys. B 66, 741 (1998)
[2] K. Schneider, et. al., OSA Tops 19, 256 (1998)
[3] G.A. Turnbull, et. al., Opt. Lett. 25, 341 (2000)