RESUMO
Thermal radiation can be substantially enhanced in the near-field scenario due to the tunneling of evanescent waves. Monolayer graphene could play a vital role in this process owing to its strong infrared plasmonic response, however, which still lacks an experimental verification due to the technical challenges. Here, we manage to make a direct measurement about plasmon-mediated thermal radiation between two macroscopic graphene sheets using a custom-made setup. Super-Planckian radiation with efficiency 4.5 times larger than the blackbody limit is observed at a 430-nm vacuum gap on insulating silicon hosting substrates. The positive role of graphene plasmons is further confirmed on conductive silicon substrates which have strong infrared loss and thermal emittance. Based on these, a thermophotovoltaic cell made of the graphene-silicon heterostructure is lastly discussed. The current work validates the classic thermodynamical theory in treating graphene and also paves a way to pursue the application of near-field thermal management.
RESUMO
Analogy optical devices (AODs) able to do mathematical computations have recently gained strong research interest for their potential applications as accelerating hardware in traditional electronic computers. The performance of these wavefront-processing devices is primarily decided by the accuracy of the angular spectral engineering. In this Letter, we show that the multilayer technique could be a promising method to flexibly design AODs according to the input wavefront conditions. As examples, various Si-SiO2-based multilayer films are designed that can precisely perform the second-order differentiation for the input wavefronts of different Fourier spectrum widths. The minimum number and thickness uncertainty of sublayers for the device performance are discussed. A technique by rescaling the Fourier spectrum intensity has been proposed in order to further improve the practical feasibility. These results are thought to be instrumental for the development of AODs.
