View article

Planar waveguides were made from a linear epoxy copolymer of bisphenol-A diglycidyl ether and amino-nitro-tolane. The refractive indices, n_TM and n_TE, and the electro-optic coefficients, r_33 and r_13, of the poled nonlinear-optical 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 ν (0 ≤ ν ≤ 1), we develop a simple model that can account for electro-optic coefficient ratios ranging from 3 to 6.