Nano-optics for atomic-scale optical resolution. (General Developments).

Theoretical simulations have been performed at NIST to explain the extreme, atomic-scale optical sensitivity obtained in recent nano-optics experiments that probe atomic steps on silver surfaces.

Nano-optics is a rapidly emerging field of optics. One of its primary goals is the development of optical microscopy at the nanoscale. Nanoscale resolution beats the wavelength-scale limits imposed by diffraction-limited, classical optics by a factor of 100. This super-resolution is critical for optical measurements of the nano/bioworld.

A multinational collaboration involving researchers at NIST, in Germany, and Sweden, investigated electromagnetic coupling on an atomic scale. Details were published recently in Physical Review Letters. Light emission from a scanning tunneling microscope was used to investigate the electromagnetic coupling between a metal tip and a metal surface. Experiments performed by our collaborators in Germany showed that atomic-scale modifications of the tip-sample region caused observable spectral shifts of the measured fluorescence. This exquisite sensitivity was demonstrated by probing a monatomic step on a silver surface and by variations due to atomic-scale changes in tip-sample distance. For sharp tips, the electromagnetic coupling was confined to a lateral range of a few nanometers, a factor of 100 better than the diffraction limit of conventional optics. The new calculations performed at NIST show that coupling between the probe and resonant plasmons localized at sample boundaries provide this atomic-scale opt ical sensitivity.

CONTACT: Garnett Bryant, [phone]; garnett. [e-mail].