Abstract: A process that lends itself to automation for producing multi-layer second-order nonlinear optical polymer (NLOP) thin films by the forming of a polycation layer containing an NLO-active cationic polymer, having non-centrosymmetric chromophores, on a substrate followed by the forming of a polyanion layer, also having non-centrosymmetric chromophores, on the polycation layer. A predetermind number of the polycation and the polyanion layers may be alternated upon the surface as well as one or more buffer layers. An added benefit is the formation of an ultra-smooth surface of the same order of roughness as the substrate upon which the layers are formed.