🔬🌟 Third-harmonic generation (THG) microscopy is a label-free 3D biological tissue imaging technique that can be combined with multiphoton fluorescence. While THG images are mostly used to get morphological information, the THG process can be enhanced in the presence of absorbers. This property could be used for selective imaging, but it is underutilized because it is poorly characterized in biological contexts. In this study, we analyze the THG spectra of 3 pigments: hemoglobin in red blood cells, pteridines in zebrafish xanthophores, and melanin in human hair. We find that all of these pigments exhibit resonances resulting in strong, wavelength-dependent THG responses. We also show that third-order sum-frequency generation (TSFG) imaging using a dual-output excitation laser produces "color THG" images that distinguish different structures. -> Wavelength-resolved THG appears to be an interesting approach for pigment-sensitive in situ imaging.
Congrats to Stella Dees and co-authors, Julia_Ferre_Ortas, Pierre Mahou Willy Supatto, Nicolas_Olivier and Emmanuel Beaurepaire Thanks funders European Research Council (ERC) ANR (Agence nationale de la recherche)
