Large photoinduced birefringence in an optically nonlinear polyester polymer

Abstract

A nonlinear optical polyester with disperse red side groups exhibited a stable photoinduced birefringence, from 0.14 at 850 nm to 0.21 at 633 nm, after exposure to linearly polarized short-wavelength visible or ultraviolet light. Thin-film wave plates, birefringent diffraction gratings and waveguides were written in this polymer using photoexposure. Thin- film wave plates of <1 μm thickness showed ≳π/4 phase delay and good temporal stability. A 9:1 diffraction efficiency ratio of the two polarization eigenmodes was measured from thin birefringent gratings. This ratio is in good agreement with the theoretical prediction obtained using a simple three-level model.