Electromagnetic response of an electron gas in one-dimensional quantum wires

The theory of the electromagnetic response of an electron gas in quasi-one-dimensional (1D) quantum wires to a spatially modulated electric field of incident light is developed in the random-phase approximation. In a 1D electron gas in a weak magnetic field, the incident light polarized along the wire and modulated across the wire is absorbed by both single-particle and collective excitations. The coefficient of light absorption by single-particle excitations does not depend on B, while the coefficient of light absorption by plasmons is proportional to ${\mathit{B}}^2$. It is shown that, in the case of a parabolic confining potential of the wire, the spatial modulation of the incident light due to the diffraction at a mesa-etched structure allows observing higher plasmon modes that are otherwise forbidden.