Erasure effect of the reading beam on the decay process of χ(2) in all-optical poling

We have studied the effect of the reading beam on the decay process of the photoinduced second-order susceptibility chi((2)) in both the guest-host system (disperse red I-doped polymethyl methactrylate) and the side-chain system (disperse red 19-functionalized polyimide polymer). Both experimentally and theoretically, we have proved that the reading beam has the erasure effect on the decay process, that is, chi((2)) decays faster in the high intensity than in the low intensity of the reading be:un. Furthermore, the relationship between the time constant re of the slow component of the decay process and the intensity of the reading beam I-1.06 is derived from the theoretical equations, which is fitted well with the experimental results. Based on the fitting parameters, we also compare, quantitatively, the thermal-induced orientational diffusion of trans- and the quantum efficiency of trans-to-cis photoisomerization in the two systems.