Role of electron relaxation time in the resonance behavior of a graphene strip grating in a slab

We consider numerically the scattering and absorption of the THz-range H-polarized plane wave by an infinite grating of coplanar graphene strips placed into a dielectric slab. Our accurate treatment is based on the singular integral equation (IE) for the electric current on elementary strip and its projection to the set of orthogonal polynomials, which are eigenfunctions of the static part of the problem. The resulting numerical algorithm possesses guaranteed convergence and controlled accuracy of computations including the vicinities of sharp resonances. Reflectance, transmittance, and absorbance by a slab with a graphene-strip grating are studied as functions of graphene's electron relaxation time and other parameters. We show that the electron relaxation time has the strongest effect on the resonances on the surface-plasmon modes, while those on the grating modes and the slab modes remain intact.