Two-photon emission of R6G at various excitation laser wavelengths

Rhodamine 6G (R6G) is a very popular dyes for biomedical application due to its strong emission. Our previous work showed that the emission of R6G upon blue light excitation shifted due to concentration. In biomedical applications, infrared light excitation is usually used to reduce tissue damage. Therefore, in this work, optical properties of two-photon of R6G have been conducted for various dye concentrations. Excitation sources were 750, 800, 850, 900, 950, and 1000 nm femtosecond laser. We found that emission spectra of R6G shift a few nanometer wavelengths due to concentration and the dimer effect. We also observed that three excitation sources were able to generate two-photon emissions of R6G. We also discussed the dimer effect in the shift of R6G spectra. This work will give a hint to the biomedical application that uses R6G.