Ultrafast broadband Fourier-transform CARS spectroscopy at 50,000 spectra/s enabled by a scanning Fourier-domain delay line

We propose and demonstrate a coherent Raman scattering (CRS) spectroscopy technique capable of acquiring 50,000 broadband Raman spectra/s. This ultrafast spectral acquisition is realized by employing a Fourier-domain delay line based on a rapidly rotating polygonal mirror array as an optical path-length scanner in a broadband Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy platform. We provide a theoretical description of the proposed FT-CARS spectroscopy technique while also presenting its proof-of-concept demonstration on a liquid toluene sample. Our use of a 54-facet polygonal mirror array rotating at 916 rotations/s achieves a record high scan rate of 50,000 CARS spectra/s, covering most of the molecular fingerprint region (200-1430 cm−1) with a high resolution of 4.2 cm−1. This ultrafast broadband CRS technique is expected to be of great use in applications where high-throughput screening or real-time monitoring of unknown samples with high specificity is required, such as single-cell analysis and biomedical imaging.