Everyone knows the problems and the image incandescent light bulbs face. The most grave one is definitely the really bad energy efficiency. Their light emission is done by heating up a filament (mostly tungsten) to 2700 °C. The filament then glows bright white, and its spectrum resembles a black body spectrum a very broad spectrum of light that provides a warm look and a faithful rendering of all colors in a scene. But more than 95% of the energy put into the wire is wasted, predominantly as heat.

A group at MIT showed in a recent publication in Nature Nanotechnology (doi:10.1038/nnano.2015.309) that one could enhance the energy efficiency of the incadescent light bulbs by putting a material around it that reflects most of the infra-red radiation back to the wire, so that it can be re-absorbed and re-emitted as visible light. The targeted efficiency of such a lamp would be at around 40%. 

The working principle of such a reflecting layer would be to reflect the infrared light but leave all other (especially visible) light through.

The researchers used therefore a so-called photonic crystal structure. Their achievement is that this photonic crystal works for a wide frequency range and a large range of angles.

The implications of their research is more broad than only for the renaissance of a known light source. There are possibilities also for other energy-conversion schemes such as in thermovoltaics.