Besides Fermi energy, the resonant wavelength can also be
shifted by changing the period L of the grating. In Fig. 3(b), the
absorption spectrums for three different grating periods are
shown. We can see that the resonant wavelength increases as
the period of the grating becomes larger. In the simulations, the
relaxation time of graphene is kept constant and hence the intrinsic
loss rate c0 is unchanged, but the thickness of the substrate are
varied to ensure the complete absorption condition c0 = c1 can be
meet. The results in Fig. 3(a) and (b) suggest that we can design
a device working at a desired spectrum by choosing the grating
period so that the complete absorption occurs at the center of
the spectrum, and the other part of the spectrum can be attained
by dynamically tuning the Fermi energy of graphene.
At last, it is worthwhile to point out that the variation of resonant
wavelength with Fermi energy and grating period can be analytically
calculated by the dispersion relation of graphene
plasmonic waves [13,15].