Singularities in the absorption spectrum of guided TM modes in metal–dielectric heterostructures with narrowgap electronic excitation of a buffer layer

A theoretical investigation is made of the absorption spectrum of guided TM modes in a four-layer planar metal—dielectric waveguide heterostnicture with narrow-gap electronic excitation of a buffer layer in the case when the electronic transition frequency is close to the frequency of a resonance between the guided TM modes in a three-layer dielectric wave-guide and a surface plasmon. It is shown that two types of singularity–dips (antiresonances) and shifted lines–may appear in the absorption spectrum of the guided TM modes of a four-layer heterostnicture. Potential integrated-optics applications of the predicted effect are considered.