Growth mechanism of second harmonic generation of optically poled disperse red 1/polymer films

The writing process in the formation of chi((2)) gratings for disperse red 1 (DR1)/polymethylmethacrylate film at room temperature is investigated. The writing laser power and film thickness dependence for the growth of the second harmonic generation (SHG) intensity in optically poled films is delineated. The effective growth rate of the SHG intensity is shown to be proportional to the fourth power of the fundamental laser intensity. This result is not in agreement with the existing theory. A model to account for the experimental result associated with the writing process is proposed. The dependence of the induced SHG intensity on the film thickness dependence is also studied. An equation that can adequately describe the dependence on the fundamental laser intensity and the film thickness for the effective growth rate of the SHG intensity is provided. (c) 2005 American Institute of Physics.