Photoinduced molecular alignment relaxation in poled electro-optic polymer thin films

Abstract

The photoinduced nonlinearity decay in poled nonlinear optical polymer, polyurethane/Disperse Red 19, films was studied at wavelengths from 543 to 1320 nm. Electro-optic gratings and waveguide modulators were used in measuring and monitoring material’s nonlinearity. No photoinduced nonlinearity decay was detected at near infrared wavelengths. However, the photoinduced relaxation rate increased approximately 5 orders of magnitude from 670 to 543 nm, as the excitation wavelength approaches π-π* transition of the chromophores. The photoinduced chromophore reorientation was identified as the dominant relaxation mechanism.