Photosynthetic Pigments and Protein Complexes as Dyes For Third Harmonic Generation Microscopy

The third-order nonlinear optical properties of a number of photosynthetic pigments including phycobilins and flavonoids as well as light-harvesting pigment-protein complexes such as phycobiliproteins were investigated because these pigments and light-harvesting pigment-protein complexes are promising candidates for applications in high-speed optical switching, optical modulators, optical computing, and as contrast agents in nonlinear optical microscopy. The third-order nonlinear optical susceptibility values of these pigments and pigment-protein complexes were obtained at 1030 nm wavelength using the third harmonic generation ratio technique, combined with index of refraction measurements. The third-order nonlinear optical susceptibility values of flavonoids, phycobilins and phycobiliproteins decreased with increasing concentration, while the magnitudes of the third-order nonlinear optical susceptibility values with concentration of phycobilins and phycobiliproteins was much larger than flavonoids.