Grating translation technique as a tool for monitoring phase shifts during holographic recording in azo-polymers

Abstract

Grating translation technique, elaborated for photorefractive materials, can be used for determination of amplitude and phase grating contributions to light diffraction efficiency after holographic recording in photochromic polymer films. Here, we report application of this technique to in situ analysis of the formation of light inscribed diffraction gratings in azo-functionalized polymers. This technique allows for monitoring amplitudes and phase shifts between phase and amplitude gratings during holographic recording. For the investigation, we chose two azo-polymers with identical azo-substituents and characterized by qualitatively different temporal evolutions of grating build-up process during holographic recording with light s-s polarization geometry. The observed differences in grating recording kinetics for these polymers are explained by the difference in dynamics of build-up of amplitude and phase gratings including surface relief gratings and the spatial phase shifts between them and light interference pattern. Methodology described in this work could be applied to systems in which complex mechanism of refractive index changes upon light illumination are expected.