Binary Grating of Subwavelength Silver and Quantum Wires as a Photonic-Plasmonic Lasing Platform With Nanoscale Elements

This paper considers the scattering of an H-polarized plane wave by a freestanding periodic grating that contains two circular cylinders on each period, one made of silver and the other of dielectric. If such a grating is made of deeply subwavelength wires, the reflection and transmission coefficients demonstrate both plasmon and grating resonances. To clarify them, we also discuss the scattering by similar gratings made of either silver or dielectric wires only. However, the main attention is paid to the associated lasing eigenvalue problem for the dielectric cylinders pumped to become quantum wires, i.e., to obtain a “negative-absorption” complex refractive index. The analysis is done using a meshless analytical-numerical method with guaranteed convergence. The computations show that, in this composite periodic cavity, material thresholds of lasing for the grating modes can be much lower than for the plasmon modes.