Fig. 2: Schematic of the FIRE system.

a Architecture of FIRE. PBS, polarization beam splitter; DM, dichroic mirror; GMS, galvanometer scanner; MFI, multimode fiber I; FA, fiber array; AC, achromatic lens; G, grating; M, mirror; FAB, fiber array bundle; AMP, amplifier; AFG, arbitrary function generator; NI, National Instrument acquisition card; HAC, high-speed acquisition card; and SiPM, silicon photomultiplier. b Paraxial Littrow spectrometer of FIRE. In the real system, the two input fibers are located on two sides of an FA to achieve paraxial projection. c FIRE-measured full-band Raman spectrum (−300-4300 cm−1) of a mixed sample (H2O:D2O:DMSO = 2:1:1 in volumetric ratio) at 100 ms. d, Raman spectrum of pure DMSO obtained within 1 ms. The spectrum in red shows the dark noise generated within 1 ms when the excitation laser is off.