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Excited-state absorption optical limiting of a novel organic polymer

The optical limiting response and excited-state absorption properties of a novel organic polymer (poly(5-2-methythio-4- methyl-5-pyrimidinyl)-2,4-pentadine-1-ol)-p-toluene sulfinate) in chloroform solvent have been investigated and its solutions almost have no absorption in visible spectral range. A Nd:YAG laser source with 8-ns/21-ps pulse width and 532-nm wavelength was employed. The pulse-width-dependent measurements indicated that the optical limiting mechanism is excited state absorption along with nonresonant two photon absorption. The open aperture Z-scan was also performed to measure the molecular excited state absorption coefficient. The nanosecond optical limiting behavior of the various concentration solution samples with nominal transmissions of 87%, 56% and 26% have been measured as a function of the beam fluence. The theoretical fitting result of excited state cross section can be fitted on the mode that excited-state absorption is the predominant mechanism causing the observed optical limiting behavior.