Abstract: Coatings for optical devices, such as beamsplitters, are provided. The coatings include at least one bilayer of a layer of a material having an index of refraction n1 in contact with a layer of a material having an index of refraction n2 and an uppermost layer of a material having an index of refraction n3 over the bilayer, wherein n3>n2>n1. The bilayer(s) can be composed of BaF2 and KRS5. The uppermost layer can be composed of Ge. Certain coatings provide beamsplitters which exhibit highly efficient emission over broad spectral ranges.

Abstract: A semiconductor laser and light emitting device is defined. The device comprises an electron injector and an active region adjacent to the electron injector. The active region includes at least one deep quantum well with barrier layers adjacent to either side of the quantum well or wells such that electrons injected from the electron injector into a high energy level of the quantum well relax to a lower energy level with the emission of a photon and are transmitted out to a region beyond the last barrier layer of the active region. The electron injector includes quantum well layers. The bottom of each deep quantum well or wells in the active region is lower in energy than the bottoms of the quantum well layers in the electron injector. The device may further comprise at least two stages wherein each stage contains an electron injector and an active region.