Peter Krötz

16.5μm quantum cascade detector using miniband transport

The authors report on an InP based photovoltaic quantum cascade detector operating at 16.5μm and using miniband-based vertical transport. This concept allowed the construction of a longitudinal optical phonon extraction stair with two rungs without touching on a high device resistance. At 10K, they observed a responsivity of 1.72mA∕W and a Johnson noise limited detectivity of 2.2×109 Jones. Altogether, this design resulted in detection at temperatures of up to 90K with a lower bandwidth limit of 200MHz imposed by the measurement setup.

Fully reflective external-cavity setup for quantum-cascade lasers as a local oscillator in mid-infrared wavelength heterodyne spectroscopy

To our knowledge we present the first experiments with a fully reflective external-cavity quantum-cascade laser system at mid-infrared wavelengths for use as a local oscillator in a heterodyne receiver. The performance of the presented setup was investigated using absorption spectroscopy as well as heterodyne techniques. Tunability over approximately 30 cm(-1) at 1130 cm(-1) was demonstrated using a grating spectrometer. A continuous tuning range of 0.28 cm(-1) was verified by observing the spectra of an internally coupled confocal Fabry-Pérot interferometer and the absorption lines of gas phase SO(2). In a second step the output from the system was used as a local oscillator signal for a heterodyne setup. We show that spectral stability and side mode suppression are excellent and that a compact external-cavity quantum-cascade laser system is well suited to be used as a local oscillator in infrared heterodyne spectrometers.

Probing Stellar Atmospheres with Ultra‐High Resolution Infrared Heterodyne Spectroscopy

We present astronomical applications of the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS). Measurements of planetary atmosphere dynamics of Mars and Venus with an accuracy of <10 m/s, taken over the last two years, demonstrate the capabilities of heterodyne spectroscopy in the mid infrared.High spectral resolution of up to R = 107 enables us to fully resolve molecular or atomic lines and to deduce three dimensional structures. Precise measurements of stellar winds are also feasible with THIS. Furthermore, large scale convection in stellar atmospheres might be a target for ultra‐high resolution spectroscopy. Other possible applications include the measurement of stellar magnetic fields by observing the Zeeman splitting of molecular lines (e.g. Mg I), or velocity resolved observations of Ne II in circumstellar discs.