Refractive-index and thickness sensitivity in surface plasmon resonance spectroscopy.

The sensitivities of surface plasmon resonance spectroscopy were examined at incident angles of 66-76 deg. The sensitivities were calculated for various refractive indices of liquid samples and for various thicknesses of deposited dielectric thin layers. Furthermore, the sensitivities were confirmed experimentally. The experimentally measured refractive indices and thicknesses were 1.3311-1.3463 and 0-89 nm, respectively. From these results it was demonstrated that the sensing system showed higher sensitivities with smaller incident angles. For example, the sensitivity for a refractive index at a 66 degrees incident angle was seven times larger than that at 76 degrees. It was also demonstrated that the resonant wavelength has a linear relation to the refractive index and the thickness at refractive indices and thicknesses of 1.33-1.345 and 0-100 nm, respectively, except for a 66 degrees incident angle.