Linear and Second-Order Nonlinear Optical Properties of Urethane-Urea Copolymers

Nonlinear optical (NLO) polyurethanes have been intensively studied to develop electro-optic devices, because they have not only large second-order NLO coefficients (d33) but also good temporal stability of d33 at room temperature [1,2]. We have reported that introducing urea groups into main chains of polyurethanes, namely urethane-urea copolymers, improves the temporal stability at elevated temperatures [3]. The copolymers have many advantages, for example easiness of synthesis, relatively high intrinsic viscosity [η] (molecular weight), easiness of poling process, and applicability of photobleaching method [4]. In the present work, linear and second-order nonlinear optical properties of the copolymers are discussed.