Abstract
Spontaneous Raman microscopy reveals the chemical composition of a sample in a label-free and non-invasive fashion by directly measuring the vibrational spectra of molecules. However, its extremely low cross section prevents its application to fast imaging. Stimulated Raman scattering (SRS) amplifies the signal by several orders of magnitude thanks to the coherent nature of the nonlinear process, thus unlocking high-speed microscopy applications that provide analytical information to elucidate biochemical mechanisms with subcellular resolution. Nevertheless, in its standard implementation, narrowband SRS provides images at only one frequency at a time, which is not sufficient to distinguish constituents with overlapping Raman bands. Here, we report a broadband SRS microscope equipped with a home-built multichannel lock-in amplifier simultaneously measuring the SRS signal at 32 frequencies with integration time down to 44 µs, allowing for detailed, high spatial resolution mapping of spectrally congested samples. We demonstrate the capability of our microscope to differentiate the chemical constituents of heterogeneous samples by measuring the relative concentrations of different fatty acids in cultured hepatocytes at the single lipid droplet level and by differentiating tumor from peritumoral tissue in a preclinical mouse model of fibrosarcoma.
Original language | English (US) |
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Pages (from-to) | 076104 |
Journal | APL Photonics |
Volume | 7 |
Issue number | 7 |
DOIs | |
State | Published - Jul 6 2022 |
Bibliographical note
KAUST Repository Item: Exported on 2022-09-14Acknowledged KAUST grant number(s): OSR-2016-CRG5-3017-01
Acknowledgements: D.P. acknowledges funding from the European Union project CRIMSON under Grant Agreement No. 101016923 and from the Regione Lombardia project NEWMED under Grant Agreement No. POR FESR 2014–2020. G.C. and T.S. acknowledge funding from the European Union project GRAPHENE Core3 under Grant Agreement No. 881603. G.C. and C.L. acknowledge funding from the King Abdullah University of Science and Technology under Grant Award No. OSR-2016-CRG5-3017-01. A.D.C. acknowledges the invaluable support and insights from Zülal Karaca throughout this research.