Direct measurement of standing evanescent waves with a photon-scanning tunneling microscope

Abstract

We present a detailed analysis of a standing evanescent wave that is caused by total internal reflection of an Ar-ion laser beam on a glass prism and investigate the coupling to a subwavelength dielectric tip of a photon-scanning tunneling microscope that is raster scanned at a close distance over the prism surface. The intensity of the evanescent field is spatially modulated with a period of 239.2 nm. It decays exponentially with a constant of 103.9 nm with increasing distance from the prism surface. Precise measurements of the standing evanescent wave can be used to calibrate the scanner and permit one to determine the spatial resolution and the coupling efficiency of the tip.