(Solved): The dispersion curve of surface plasmon polariton (SPP) on a planar metal-air interface is shown in ...
The dispersion curve of surface plasmon polariton (SPP) on a planar metal-air interface
is shown in the figure below, together with the linear dispersion of light propagating in free space.
(a) For the SPP wave at an angular frequency of 4.2 × 1015rad/s, its wavevector parallel to the
interface is given in the figure. What is the wavelength of this SPP wave?
(b) Suppose now we want to use the prism coupling method to excite this SPP wave with the
propagating light in the prism, what is the minimum refractive index the prism material needs
to have in order to make the coupling possible? (Hint: recall the discussion on energy and
momentum conservation).
(c) If the refractive index of the prism material is 3, how large the incident angle should be to
excite the SPP wave?
(d) If we want to use the same method to excite a SPP wave at the angular frequency
4 × 1015rad/s, is the required minimum refractive index of the prism smaller or larger than
that in (b)?
