Wave-dispersed two-photon absorption ofC60

Abstract
We report the two-photon absorption (TPA) spectrum of C60 in the wavelength range λ=0.7–1.5 μm. The TPA coefficient β of the polycrystalline film shows a broad peak, with β≈25 cm/GW, around 0.95 μm and drops below 3 cm/GW at λ>1.2 μm. We find that the nonlinear absorption, and also the sign of the nonlinear refraction above and below the TPA maximum, are satisfactorily accounted for by modeling the response with a two-photon state positioned at 2.58 eV.