Figure 5.
Matching of two-photon excitation spectra of red fluorescent proteins with the optimum tissue transparency and with the wavelengths of some short-pulse laser systems. (a) Typical tissue transparency window (Ref.39, filled gray) presented as attenuation coefficient, left y-axis; 2PE brightness spectra per protein chain of tdTomato and tdKatushka2, right y-axis; and their corresponding normalized fluorescence spectra. (b) Effective laser efficiency relevant to two-photon excitation (average power squared divided by repetition rate and pulse duration) of several commercial femtosecond lasers.