Birefringent and electro-optic effects in poled polymer films

Abstract

By expanding the orientational distribution function, f(Θ,t), of molecular dipoles in terms of Legendre polynomials with spherical modified Bessel functions, in(μE/kT), as coefficients, an analytic relation between the steady-state birefringence, Δn2ω, and electrooptic coefficient, Xxxx(2)(-ω; ω, 0), for a poled nonlinear optical system is obtained. A rotational diffusion equation, with the diffusion constant, D, for the distribution function describing the onset and decay of the induced optical and electro-optic properties, is solved with the help of the recurrence relation for spherical modified Bessel functions. It is found that the onset of birefringence involves at least two time constants with rise times of 1/2D and 1/6D, while the onset of the electro-optic effect is dominated by the rise time of 1/2D. After removal of the de poling field, the birefringence and electro-optic effects are found to relax in time with different decay time constants, 1/6D and 1/2D, respectively. This occurs because of the difference in the tensor rank describing the birefringence and the electro-optic effect.