Ultrathin layer sensing based on hybrid coupler with short-range surface plasmon polariton and dielectric waveguide

A highly integrated sensor that is based on a hybrid coupler composed of short-range surface plasmon polariton (SRSPP) and dielectric waveguides was proposed for refractive index detecting of an ultrathin layer. The dependence of the coupling between the SRSPP and dielectric waveguide mode on the refractive index of the detecting layer was analyzed theoretically. For a detecting layer as thin as 1/15 wavelength, the resolution can be as high as 3.3x10(-6) refractive index units with a sensing length of only tens of micrometers.