Bleaching kinetics of indoly‐benzylfulgimide in PMMA

Abstract

Indoly‐benzylfulgimide belongs to the photochromic fulgide family and follows photochemical first order kinetics. Its bleaching kinetics is investigated at 633 nm and 640 nm by spectroscopy, by the time dependence of transmission and of diffraction from holographically induced gratings. The non‐exponential decay law resulting for diffraction experiments with a Gaussian beam profile is calculated and verified experimentally. For a quasi‐homogeneous beam profile the time constant determined from diffraction decay is half the one for absorbance decay. The photochemical reaction rate of indoly‐benzylfulgimide in PMMA is (3.9 ± 0.3) cm2/J at 650 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Improvement of the diffraction efficiency of isotropic and anisotropic gratings in Fulgide film by auxiliary light

“…[1][2][3][4] For ordinary holographic storage applications, same with all the other photochromic materials, there exits an overshooting peak (optimal exposure E opt ) in the diffraction efficiency growing, which then decays to a lower permanent level, because of the diminishing of fringe contrast caused by a photochemically active readout beam, unequal intensities of object and reference waves and the nonlinear saturation effects of photochromic process. [2][3][4][5] And then, because of the bistable state characteristic of the fulgide films, the diffraction efficiency will also decay to zero. [5] It is known that this overshooting phenomenon in ordinary holograph recorded in photochromic materials can be prevented by using an auxiliary light, which has the effect of molecular back-conversion photo chrome.…”