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A heat-powered emitter can sometimes exceed the Planck thermal-emission limit. We clarify when such super-Planckian emission is possible, arguing that far-field super-Planckian emission requires a distribution of energy that is not consistent with a unique temperature, and therefore the process should not be called ‘thermal emission’.
The field of flat lens research brings innovative nanophotonic design concepts to the world of macro-optics. However, when evaluating the performance of these lenses a lack of consistency prevents proper comparison of competing technologies. This problem can be solved by using methods developed in industry for conventional lenses.
