Reflection properties and lasing modes in the H-polarization case for an infinite chain of dielectric and silver nanowires

We study the scattering of the H-polarized plane wave by a freestanding periodic grating that contains two circular cylinders on a single period, one made of silver and another dielectric. The reflection and transmission coefficients for such a grating demonstrate several types of resonances including plasmons and grating resonances. Besides, we analyze the associated eigenvalue problem where the dielectric cylinders are so-called quantum wires, i.e. have “negative-absorption” or “active” refractive index. The comparison of eigensolutions for the grating modes of two active chains, one with and another without silver elements shows that the thresholds of lasing are higher in the former case, apparently because of the losses in silver.