Theory of prism-coupled light emission from tunnel junctions

Abstract

We have developed a theory of light emission from smooth tunnel junctions through a coupler prism. This method of light emission does not depend on the surface roughness of the junction for the emission mechanism by surface-plasmon polaritons, and allows direct emission by the fast mode. The theory follows the Green’s-function formalism developed by Laks and Mills and uses the same assumed form of current fluctuations in the junction. The prediction of this theory for the angle dependence of the emission intensity agrees well with the experimental result, but the calculated emission spectra at several angles do not agree with the experimental results. From the fact that the observed spectra show a well-defined peak in the frequency region in which the slow mode is very strongly excited, we conclude that an important process that produces the observed spectra involves the conversion of the slow mode to the fast mode mediated by residual surface roughness.