Achromatic optical collector for a micro-integrated plasma emission-spectro-scopic gas sensor

We report about the progress of a research project that aims at the construction of a planar micro-integrated sensor head for the chemical analysis of tiny gas samples by means of plasma emission spectroscopy. The idea is to integrate several heterogeneous steps of this detection principle on a common micro-technological platform, namely the plasma generation, the excitation of the analyte gas, the collection of the emitted radiation, and the fiber-based coupling into a spectrometer where the characteristic emission spectra are detected and identified. The sensor head consists of an optically transparent planar wafer with a tiny hole in the center and thin-film electrodes on both sides that act as micro-hollow cathode plasma chamber. The analyte gas is blown through this hole in which a glow discharge takes place. Our particular focus lies on the collector functionality and a novel reflective optical systems design that is achromatic for all relevant wavelengths. We will present optical perfomance estimations on the basis of computational models and discuss manufacturability issues.