Lasing Thresholds of Plasmon and Grating Modes of Coated Silver Nanowire Gratings

We study the electromagnetic field in the presence of a freestanding periodic grating of nanowires made of silver and covered with dielectric shells. In the H-wave scattering problem, reflection and transmission coefficients for such grating demonstrate a cocktail of various types of resonances including plasmon-mode and grating-mode ones. In the Lasing Eigenvalue Problem, where the shells material possess the gain characterized by the negative imaginary part of refractive index purposed to compensate absorption, we determine the wavelengths and the threshold values of gain of these modes.