Photon tunneling microscopy

Abstract

Photons incident to a total internal reflection surface that is also the object plane of a reflected light microscope will tunnel through a submicron gap in the presence of a dielectric sample. Tunneling increases exponentially with sample height for a homogeneous refractive index and is quantified by empirical calibration to a known geometry. Video photometry of the grays scale tunneling image is converted by a three-axis oscilloscope into a real time 3-D topographic image featuring variable perspective. Vertical resolution is detector-limited to less than a nanometer over a field depth, also detector-limited, of ~0.75lambda; lateral resolution is enhanced to ~0.29lambda. Photon tunneling images of diamond turned surfaces, optical data structures, a polished optical surface, and microlithographic structures are among those presented. Comparison and correlation with other methods for measuring surface topography in this regime are briefly discussed.