The Next Generation of IR Spectroscopy: EC-QCL-Based Mid-IR Transmission Spectroscopy of Proteins with Balanced Detection

In 2020 scientific group from the Technische Universität Wien and VIGO Photonics published in American Chemical Society (ACS Publications) an article where they describe a system for analysis of proteins based on VIGO product, thanks to which they achieved results that by almost an order of magnitude better than other state-of-the-art mid-IR-based techniques.

Researchers introduced a new mid-IR transmission setup for recording protein spectra in the amide I and II region by using an external cavity-quantum cascade laser (EC-QCL) and a mercury cadmium telluride (MCT) balanced detection module produced by VIGO Photonics. Two individual thermoelectrically cooled mid-IR MCT detectors were precisely matched regarding their transimpedance, voltage responsivity, and detectivity to achieve a high common mode rejection ratio (CMRR). The used detector provides individual outputs for the intensity levels of the two beam paths as well as the balanced channel, which corresponds to the difference between the two channels. This balanced detection approach enables to reduce the intensity noise inherent in the laser emission spectrum.

Thanks to the balanced mid-IR detection module produced by VIGO Photonics and EC-QCL, scientists revealed noise levels better by a factor of up to 20 in balanced detection mode compared with single-channel measurements. The results enable the use of the system where the protein concentration at certain process steps are below the range accessible by conventional FT-IR (Fourier transform infrared) spectroscopy.

Link to the article