We have observed mode conversion in the structure that supports two surface-plasmon polaritons. This mode-conversion phenomenon shows up as the emission from both modes, when either of the modes is excited, and is due to intrinsic roughness of the interfaces. We present an outline of a first-order (in roughness) Green’s-function-based theory that yields a simple expression for the scattering cross section and which is in good agreement with the experimental data. Implications of these results for light-emitting tunnel junctions are discussed.

• Received 3 November 1986

DOI:https://doi.org/10.1103/PhysRevB.36.3052