A novel high efficiency electro-optic polymer light modulator based on waveguide-coupled surface plasmon resonance (WCSPR) is presented. The modulator consists of a five-layer system: dielectric layer/metal film/electro-optic (E-O) polymer layer/metal film/air. By combining WCSPR based on attenuated total reflection (ATR) method and Pockels effect from poled E-O polymer, we demonstrate that this kind of modulator operated with less applying modulation voltage, less optical insertion loss, and easy alignment compared to other light modulation techniques. Also, in this paper the theoretical derivation of WCSPR, the optimum design concerning the relation between the efficiency of modulator and E-O layer thickness, and the fabrication process of the E-O polymer light modulator are presented. This modulator is shown to allow a greater degree of modulation for a given voltage with working point chosen near the midst of WCSPR mode in the visible range.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.