Time-stretch infrared spectroscopy

Abstract: Improving spectral acquisition rate of broadband mid-infrared spectroscopy promises further advancements of molecular science and technology. Unlike the pump-probe spectroscopy that requires repeated measurements with different pump-probe delays, continuous spectroscopy running at a high spectral acquisition rate enables transient measurements of rapidly changing non-repeating phenomena or statistical analysis of a large amount of spectral data acquired within a short time. Recently, Fourier-transform infrared spectrometers (FT-IR) with rapid delay scan mechanisms including dual-comb spectrometers have significantly improved the measurement rate up to ~1 MSpectra/s that is fundamentally limited by the signal-to-noise ratio. Here, we overcome the limit and demonstrate the fastest continuous broadband vibrational spectrometer running at 80 MSpectra/s by implementing wavelength-swept time-stretch spectroscopy technique in the mid-infrared region. Our proof-of-concept experiment of the time-stretch infrared spectroscopy (TS-IR) demonstrates broadband absorption spectroscopy of phenylacetylene from 4.4 to 4.9 {\mu}m (2040-2270 cm-1) at a resolution of 15 nm (7.7 cm-1) with a superior signal-to-noise ratio of 85 without averaging and a shot-to-shot fluctuation of 1.3%.