Electro-optic coefficients in electric-field-poled polymer waveguides

Planar waveguides were made from a linear epoxy copolymer of bisphenol-A diglycidyl ether and amino-nitrotolane. The refractive indices, nTMand nTEand the electro-optic coefficients, r33and r13of the poled nonlinearoptical polymer films were determined by measurements of the waveguide modes of these films at a wavelength of 632.8 nm, and the results are reported for both electrode and corona poling. The ratio of the second-order susceptibilities was found to exceed significantly the theoretically expected value of 3. The restricted motion of the nonlinear chromophores during poling provides a possible explanation of this discrepancy. Introducing a restriction parameter v (0 ≤ v ≤ 1), we develop a simple model that can account for electro-optic coefficient ratios ranging from 3 to 6. © 1991 Optical Society of America.