Incoherent Fourier transform spectroscopy with room-temperature coverage from NIR to THz

Despite the broadband nature of thermal light sources, optical spectroscopy over multiple spectral bands simultaneously remains challenging. Here, we demonstrate a practical Fourier transform infrared spectrometer (FTIR) that achieves room-temperature spectral coverage from 1 to 50 μm (300–6 THz) in seconds using a single set of optics, with the long wave cutoff extendable to 90 μm (3.3 THz) and the short wave to the ultraviolet (0.39 μm). The interferometer employs a diamond plate beam splitter and windowless lithium tantalate (LTO) detector to probe the spectrum of combined incoherent sources operating at different temperatures. Applications of the instrument in modern chemometry, material science, and medicine are envisioned.