Measurement of dyes two-photon absorption cross-sections used for photodynamic therapy

To overcome the limitations of photodynamic therapy, the use of two-photon excitation of dyes is suggested. This enables an increase in the therapeutic impact depth on the tumor without surgical operation and a decrease in the light stress. This paper examines the cross-sections of two-photon absorption of a series of dyes used in medicine on the laser wavelength Ti:sapphire. The method of two-quantum etalon was used based on the comparison of the intensity of the two-photon excited fluorescence (TPEF) of the agent investigated with the intensity of etalon TPEF with known cross-section of the two-photon absorption under similar conditions of excitation. To obtain the absolute value of the cross-section of the TPEF agents, it is necessary to carry out recalculations that take into account the values of the fluorescence quantum input of the corresponding dyes.