Two-photon cross-sections of the photosensitizers m-THPC and m-THPP in the 1.05–1.45 μm range

• The open-aperture z-scan technique is applied to measure two-photon absorption.
• The studied tumor photosensitizers show good two-photon absorption at 1.05–1.45 μm.
• The two-photon absorption is lower for circular than for linear polarized light.

The two-photon absorption of the photosensitizers 5,10,15,20-tetrakis(m-hydroxyphenyl) porphyrin and the corresponding chlorin has been studied in the near infrared (IR) range using open-aperture z-scan technique. We found cross sections of 10–40 GM in the Q-band region, comparable to values in the Soret-band. Both photosensitizers are promising candidates for IR two-photon photodynamic therapy given the better penetration of IR light into tissue.