9 - Photoisomerization in Polymer Films in the Presence of Electrostatic and Optical Fields

Abstract

The polymer environment plays an important role in the mobility of isomers. This chapter presents a nonlinear optical experimental technique to probe a change in nonlinear optical properties during photoisomerization in polymer thin films. It is noted that electrostatic and optical electric fields manipulate the geometrical shape and orientation of isomers in the polymer film. To be relevant, the second harmonic generation (SHG) is essentially used to detect the changes in the second and third-order nonlinear properties. SHG provides detailed information of photoisomerization in a polymer film in the presence of a large electrostatic field. Electric fields can align molecules in a polymer host provided the molecules have enough mobility. Raising the temperature can increase the mobility of molecules. This mobility is commonly known as thermal-induced mobility. The process of photoisomerization itself can also increase the mobility of the isomers in a polymer host. Photoisomerization can also control the optical nonlinearities of materials that have applications in optical switching and optical storage applications.