THz semiconductor laser incorporating a controlled plasmon confinement weveguide

A semiconductor laser comprises an active region which, in response to a pumping energy, can produce a stimulated emission of radiation, and a waveguide region suitable for confining the radiation in the active material. In order to realise a laser operating at wavelengths in the far infrared region, a novel waveguide is disclosed comprising one doped layer delimited on opposite sides by interfaces capable of supporting surface plasmon modes. The latter are generated by the interaction of the radiation with the free electron charge in the layer. Such waveguide layer is doped so as to ensure high modal confinement together with a substantial suppression of the plasmon mode inside the layer, thereby minimising optical losses.