In this paper, the optical switching effects of poly(methyl methacrylate) (PMMA) composites doped with azobenzene chromophore Disperse Red 1 (DR 1) were investigated by using a 514-nm pump beam and a 632.8-nm probe beam. The factors influencing the optical switching effects, such as the modulation frequency, pump beam power and temperature, were studied experimentally. The photoinduced reversible and repeatable change in the transmittance of the probe beam of the composite system is attributed to the photoinduced anisotropy resulting from the photoisomerization of the azobenzene chromophores. (C) 2003 Elsevier B.V. All rights reserved.