A photon-recycling incandescent lighting device
TLDR:<p>This paper demonstrates quite convincingly (because the descriptions are very detailed) that the ancient Edison light bulb (i.e. with light emitted by incandescent carbon) can be revived by using modern technologies in a form that can be better than the current LED lamps.<p>The first incandescent lamps had 2 disadvantages, short lifetime and low efficiency.<p>The evaporation and oxidation of the incandescent carbon can be avoided by a structure made of carbon nanotubes that works in argon. The claimed lifetime (based on accelerated aging tests) is as good as for LEDs.<p>The low efficiency is solved by using a lossless optical filter (i.e. one that transmits the visible light and reflects back the infrared light) to prevent the heat loss from the lamp by radiation other than the useful light output.<p>This method can reach the maximum energy efficiency determined by the human vision characteristics, unlike the current LED lamps, which are unavoidably limited to a value lower than that by the losses caused by the fluorescent light conversion.<p>The design of the lossless optical filter is a difficult optimization problem due to the large number of parameters. Their solution, which is completely described in the paper, is claimed to have been found by a machine-learning algorithm.