surrounding the hot object with special nanophotonic structures that spectrally filter the emitted light, meaning that they let the light reflect or pass through based on its color. Because the filters are not in direct physical contact with the emitter, temperatures can be very high.
The researchers also redesigned the incandescent filament from scratch. In this case, they turned it into a piece that was laser-machined out of a flat sheet of tungsten, which makes it completely planar. Since a planar filament has a large area, it's efficient at re-absorbing the light that was reflected by the filter.
In the new-concept light bulb prototype, the efficiency approaches some fluorescent and LED bulbs. This could be huge for the future of light bulbs.'