Visible and near-infrared Fourier transform spectroscopy with a common-path interferometer

Optical spectrometers can be generally divided into two categories, frequency-domain and time-domain ones. The former includes compact, industrial-grade instruments that are easily available in the visible spectral range. The latter are lab-grade, bulky and fragile instruments that offer very high sensitivity and accuracy but are mainly limited to the infrared spectral region. This manuscript aims to present a time-domain device and several of its applications in which it is possible to combine some of the advantages of the two techniques, finally, bringing the advantage of Fourier Transform Spectroscopy down to the visible and near-infrared spectral regions. The device is a common-path interferometer based on birefringence. The concept is straightforward, and it is a compact, robust, and cost-effective instrument, and it has been applied in a wide range of applications. In this manuscript, the interferometer will be described from a theoretical point of view, and its capabilities will be presented applied to the measurement of fluorescence Excitation-Emission Matrix (EEM) Maps down to the ultimate sensitivity at the single-molecule level, Time-Resolved Photoluminescence (TRPL) spectra, spectral images, and the complex optical activity.