Nanoantennas refractive-index sensing

[vst98]

Why optical Nanoantennas can be used for refractive index sensing ?
Also it is not clear to me whose index is determined here, the index of material from which nanoantenna is built or the substrate on which nanoantenna is placed or the index of surrounding media ?
I would appreciate if someone gives me a clue how this works.

 

[Tarti]

Dear vst98,

I do not understand your question. Nanoantennas can in principle be used to probe their near-field for sensing, spectroscopy etc.
But if you have a statistical ensemble of small nanoantennas, you may use the Clausius-Mossotti relation to define an effective refractive index.