Abstract
The application of non–equilibrium transport techniques to narrow–gap semiconductor materials has produced practical, negative–luminescent devices. These structures apparently contravene Kirchhoff's law because they will absorb infrared (IR) radiation in a limited band without emitting it, although they are not in equilibrium. They have many potentially important applications. These include gas sensing, cold shields for IR detectors, radiometric reference sources for thermal imagers, radiant coolers, and dynamic IR scene projectors.