Fast Hyperspectral Imaging with Stimulated Raman Scattering by Chirped Femtosecond Lasers

摘要

Raman microscopy is a quantitative, label-free and noninvasive optical imaging technique for studying inhomogeneous systems. However, the feebleness of Raman scattering significantly limits the use of Raman microscopy to low time resolutions and primarily static samples. Recent developments in narrowband stimulated Raman Scattering (SRS) microscopy have significantly increased the sensitivity of Raman based label-free chemical imaging by a few orders of magnitude, at the expense of reduced spectroscopic information. Based on a spectral focusing approach, we present a fast SRS hyperspectral imaging system using chirped femtosecond lasers to achieve rapid Raman spectra acquisition while retaining the full speed and image quality of narrowband SRS imaging. We demonstrate that quantitative concentration determination of mixed chemical species can be achieved with sensitivity down to 4 mM. For imaging purposes, an entire Raman spectral data cube can be obtained within a minute. We show that mammalian cells SRS hyperspectral imaging reveals the spatially inhomogeneous distribution of saturated lipids, unsaturated lipids, cholesterol and protein. The combination of fast spectroscopy and label-free chemical imaging will enable new applications in studying biological systems and material systems.