To model the infrared wave absorption of a polar semiconductor nanowire with spatially dispersive permittivity, a new extension of the Mie theory is applied. This is achieved by imposing the usual Maxwell boundary conditions as well as appropriate additional boundary condition of the continuity of the normal component of the displacement field at the surface of the system. Examples of calculated infrared absorption spectra are presented, and it is found that by decreasing the wire radius, the main absorption peaks, due to the coupled surface plasmon–LO-phonon modes, are blue-shifted from their classical positions and two groups of subsidiary peaks, due to coupled bulk plasmon–LO-phonon modes, appear in the optical spectra of the system.
