Table 1 Comparisons between short-period nanostructure (ref.27) and long-period nanostructure (this work) under oblique incidence conditions.
Nanostructure | Long-periodicity capped nanoslits (900 and 1,200 nm) | Short-periodicity capped nanoslits (500 and 520 nm) |
|---|---|---|
Oblique induced shift | SPP mode blueshifted | SPP mode redshifted |
Effect | Decreased evanescent length of SPP mode | Increased evanescent length of SPP mode |
Sensing enhancement mechanism for small angle | None | Cavity mode coupling (Fano effect) |
Sensing enhancement mechanism for large angle | Short SPP evanescent length + cavity mode coupling (Fano effect) | Three mode couplings: substrate mode + cavity mode + SPP mode |
Spectral response | Higher wavelength sensitivity, but larger bandwidth | Sharp bandwidth for three mode coupling, high intensity sensitivity |
Major enhancement signal | Peak wavelength shift | Resonance intensity change |
