Project 1.2

This ESR project shall aim to achieve sub-ppb sensitivities for detecting the environmentally most relevant benzene molecule in gas phase. In order to achieve this goal important advances in photothermal spectroscopy (PTS) as well as in the employed lasers shall be made and combined. The planned advances with respect to PTS concern the design of a small and rugged double Fabry-Pérot interferometer with a high finesse and balanced detection schemes. We expect shot noise limited performance. A further important improvement in sensitivity will be achieved by placing the PTS set-up inside an optical cavity. This will require cooperation with ESR Project 2.4. To detect benzene as the representative target analyte for BTEX molecules, quantum cascade lasers (QCLs) are needed that measure the strong breathing vibration of these molecules. Therefore in a first step this ESR shall develop such lasers at UM. In this regard the InAs/AlSb material system represents a very interesting solution to achieve the required longwave-infrared (LWIR) emission due to the low electronic effective mass of InAs, which provides high optical gains. Up to now, room temperature operating single mode QCLs emitting in the 14-20 μm range have been demonstrated only by UM. ESR1.2 and ESR1.4 will have complementary tasks in the project. ESR1.2 will establish the specifications needed for the spectroscopy application. He/she will characterise in detail the operating properties of the QCLs designed by ESR1.4 and fabricated by UM and investigate their suitability to the application on the QEPAS setups of UM. He/she will provide a rapid feedback to the design stage for fabrication loops. At TU-WIEN this ESR will use these lasers for performing PTS-based gas sensing of benzene in standard as well as cavity enhanced setups.