A Multimodal Wide-Field Fourier-Transform Raman Microscope

Raman microscopy is a powerful technique to determine the chemical composition of a sample. The main challenge of the state-of-the-art spontaneous Raman microscopes, based on point-scanning frequency-domain detection, is the acquisition of Raman maps of large areas due to typically long pixel dwell times (0.1-1 s). The wide-field Fourier-transform (FT) microscope presented here allows rapid measurement of extended samples with ~1-µm spatial and ~23-cm^-1 spectral resolution. It is based on an ultra-stable and compact common-path birefringent interferometer, added along the detection path of a commercial microscope, which enables the parallel acquisition of spectra for all pixels of a 2D detector, significantly reducing the measurement time (10-100x faster). The time-domain approach effectively addresses another limitation of the frequency-domain technique, which is disentangling the Raman signal from the photoluminescence background, in which the Raman signal may be buried. This protocol describes how to perform hyperspectral measurements with an upgraded commercial microscope: the alignment of the illumination scheme, the criteria to choose measurement parameters, and the data analysis to retrieve and investigate spectra.