Light sheet direct Raman imaging technique for observation of mixing of solvents

The light sheet direct Raman (LSDR) imaging technique is used to obtain wide scope, simultaneous images of samples emitting Raman scattered light, without mapping their point-to-point Raman scattering intensities. A prototype system consisting of a background-free electronically tuned Ti:sapphire laser (BF-ETL), band-pass (BP) filters, and a charge-coupled device (CCD) detector is developed in the present study. The LS excitation method enables us to obtain a wide field of Raman view. The BF-ETL allows us to obtain direct Raman images with multiple Raman bands without the need for rearranging the optical settings. The system is used to observe the mixing of pure solvents: carbon tetrachloride (CCl₄) and chloroform (CHCl₃), and ethylene glycol (EG) and polyethylene glycol (PEG). LSDR images are successfully obtained within an exposure time of 0.5 s. EG and PEG, whose Raman spectra appear similar, can be distinguished clearly in the images, suggesting that the system has high spectral resolution.