High-Resolution Rotational Fourier-Transform Infrared Spectroscopy

We demonstrate a rotational optical delay line for Fourier transform infrared (FTIR) spectroscopy with simultaneous high time and frequency resolutions. Thanks to the rotational motion, the trade-off between speed and spectral resolution present in rapid-scan FTIRs is alleviated, and enables the use of high-brightness quantum cascade laser frequency combs as light sources. We demonstrate the capabilities of the delay line by resolving low-pressure methane absorption lines and tracking several absorption lines at video frame rates.