The MIT team, which published their findings in Nature Nanotechnology, wrapped the filament of their bulb in a new kind of crystalline filter that allows visible light to escape but reflects infrared light back towards the filament. Reflecting these IR wavelengths back to the filament keep it hotter (and therefore burning brighter) while consuming less electrical energy. The bulb is only at the proof-of-concept stage right now but the prototype reportedly is already roughly as efficient as many of the CFL and LED selections currently on the market.