Modeling and measuring radiation pattern of thermally stimulated infrared surface plasmon-polaritons diffracting on metal bar with rectangular wedge
- Mr. Ildus KHASANOV
- Mr. Ildus KHASANOV (Scientific and Technological Center of Unique Instrumentation of the Russian Academy of Sciences)
Surface plasmon polaritons (SPPs) on a conducting surface can be generated not only by an external source (such as a free electron laser), but also by thermal fluctuations of the density of conduction electrons within the skin layer of a metal body. This type of SPPs is called thermally stimulated. TSPPs are a kind of evanescent surface electromagnetic waves, which is inherently nonradiative, but can be converted into bulk waves on surface inhomogeneities. In particular, it is known that infrared TSPPs arriving to an edge of the metal body diffract on it and generate directional bulk radiation . Such radiation can be effectively used, for example, to create thermal sources of IR radiation, for heat exchange between metal objects and for passive thermal imaging. In the report we consider the problem of correct calculations and measurements of the TSPP radiation pattern (RP). SPP RP calculations rest on the analytical model obtained by Kotelnikov , who applied the Sommerfeld-Malyuzhinets method to calculate SPP RP for the case of rectangular conductive wedge. The model developed by him allows correct RP representation for monochromatic SPPs both in the near and far wave zones. This property of the model enabled us to generalize it to the case of broadband TSPP radiation. In the report we show that due to TSPP existence the edge of a metal body facet is a source of narrowly directed IR radiation with the black-body type spectrum. For correct measurements of RP was proposed a modified scheme of linear scanning by using two additional screens. The results obtained for the maximum intensity of the radiation from TSPPs are consistent with those obtained earlier . Namely: the contribution of TSPPs to the thermal radiation of the optically polished facet due to TSPP scattering by inhomogeneities is negligible, and the maximum of the RP is deviated from the plane of the facet by 2-3 degrees. In addition, it was confirmed that the increase in the radiation intensity at the RP maximum with increasing temperature lags behind the increase in the intensity of the thermal radiation of the given metal body. This work was supported by the Russian Foundation for Basic Research(grant 18-32-00930).
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- Gerasimov V.V., I.Sh. Khasanov, A.K. Nikitin and Ta Thu Trang «Searching for Evidences of the Surface Plasmon Nature of the Thermal Radiation Emitted from the Facet Edge of a Metal Bar». Infrared Physics & Technology 86 (2017): 52–58. https://doi.org/10.1016/j.infrared.2017.08.009