Energy transfer coupling of two-photon absorption and reverse saturable absorption for enhanced optical power limiting

We introduce a new approach to enhancing the optical power-limiting function at near-IR wavelength (≃800 nm) by coupling effective two-photon absorption in one molecule with excited-state absorption in another molecule. We experimentally demonstrate this approach by using a strong two-photon absorbing dye, AF-380, and a strong reverse saturable absorber, C₆₀. A nanosecond time-resolved experiment is used to show that energy transfer from AF-380 to C₆₀ generates triplet excitation in C₆₀ that further absorbs the pump beam to enhance the Dower-limiting function.