On the surface modes at the boundary between the media with normally and inversely populated levels

Within the COST MP0805 and COST MP0702 Actions, III-V group nitride compound semiconductors are considered under the conditions of inverse population of electron levels (or bands), or the inverse population of lattice vibration (phonon) bands. The last case (referring to terahertz photonics) is only briefly outlined, and the first case referring to visible (blue) photonics is in the main focus of the article. Aiming at experimental implications, frustrated total reflection spectra in GaN/In_xGa_1-xN heterostructures are calculated showing the possibility of resonance enhancement of the stimulated emission of light due to interface mode excitation.