Integrally formed surface plasmon resonance sensor

A surface plasmon resonance sensor includes a light source 1 0 and a polarizer 18 for producing polarized light which passes through a transparent body 12 and strikes a thin conductive film 26 disposed on the exterior surface of the body 12. The film 26 exhibits surface plasmon resonance when the light strikes the film at a resonance angle". By determining the angle at which surface plasmon resonance occurs, the refractive index of the material on the side of the film 26 opposite to the side which reflects the polarized light can be measured.