Determination of near surface refractive index of graded-index waveguides based on surface plasmon resonance

Near surface refractive index of a graded-index waveguide, which is greater than the effective index of the fundamental mode and cannot be evaluated in conventional m-line technique, is experimentally determined by employing the surface plasmon resonance technique. This nondestructive approach avoids the high degree of freedom in selecting the surface index of the profile. Subsequently, the index profile predicted in this paper are more accurate than that obtained by the conventional inverse WKB method.