Conditions for self-excitation of surface waves in an activated waveguide with a sinusoidally corrugated surface

The conditions are formulated for the self-excitation of E (and H) surface waves in an activated thin-film waveguide with a distributed feedback. An analysis is made of the possibility of stimulated emission in the case when the incident and reflected E (or H) waves are of different orders. For certain geometric and optical parameters of the waveguide the relationships obtained yield the threshold value of the gain for each of the component media of the waveguide.