Measurement of the electro-optic coefficient of polymer thin films with better spatial resolution

A method for measuring the electro-optic coefficient of polymer films on the basis of an asymmetry Fabry–Perot cavity is introduced. The sample layer is located between two aluminium layers, which are deposited on glass substrates by thermal evaporation. This layer structure is objected to a laser beam, and a variable voltage is applied to the aluminium films resulting in a modulation of the transmitted laser power. The electro-optic coefficient γ13γ13 of the poled polymer film can be calculated by evaluating the Fabry–Perot equation. The spatial resolution is tested with a polymer film that was poled by a needle corona discharge in air through a metal grating with a period of 120 μm. By scanning the sample plate in the direction perpendicular to the grating lines, the spatial resolution is also demonstrated according to the spacing of the poled structure.