Multiphoton Effects in the Polydiacetylene Poly Bis(p-Toluene Sulfonate) of 2,4-Hexadiyne-1,6-Diol (Pts)

Multiphoton absorption was investigated in single crystals of the polymer poly bis(p-toluene sulfonate) of 2,4-hexadiyne-1,6-diol (PTS). Using modified growth and polymerization techniques, high optical quality crystals were grown and their linear absorption spectrum measured. Very large four-photon absorption was measured using Z-scan with a value of α 4 =0.3 cm 5 / GW 3 obtained at 1600 nm. From the known one and two-photon absorption spectra, the three- and four-photon spectra are predicted to overlap. This leads to three-photon enhanced, four-photon absorption which is interpreted as the mechanism responsible for such large four-photon absorption.