Nonlinear ellipsometric analysis of poled organic glasses having very large electro-optic coefficients

Using modified Teng-Man reflection ellipsometry, very high linear electro-optic coefficients (r₃₃ = 250 - 300 pm/V) have been measured in thin films of poled organic glasses. The glasses consist of two chromophores designed to yield synergistically enhanced orientation during the poling process. The chromophores were ordered by the contact poling method under moderate electric fields of ∼ 0.44 MV/cm. Compared to measurements made 1-4 hours after poling, the electro-optic coefficient relaxed to a value about 15% lower in a period of one week and thereafter remained relatively stable at room temperature. We report both standard Teng-Man reflection type measurements made at a 45° angle of incidence as well as a more complete analysis of nonlinear reflection ellipsometric data as a function of angle of incidence and optical bias. The more complete analysis takes into account the properties of the multilayer stack structure of the test samples consisting of glass/ITO/NLO-organic/gold. Limitations of a simple model to analyze Teng-Man reflection data will be discussed, as well as contributions of electrochromism.