Highly sensitive waveguide sensor facilitated by a broadly tunable quantum cascade laser

We present a mid-infrared spectroscopic sensor based on a planar waveguide for highly sensitive and label-free chemical measurements in liquids, solids and paste-like materials. Our sensor design uses integrated grating couplers for stable coupling of intense mid-infrared radiation provided by an external cavity-quantum cascade laser to achieve extended interaction pathlengths and thus high sensitivities. In this work the sensor´s design and fabrication are outlined. Additionally, measurements for the characterization of the laser are shown. A first sample measurement was performed to demonstrate the sensitivity of the sensor in comparison with attenuated total reflection FTIR spectroscopy.