OPTICAL-PROPERTIES OF SILICON-NITRIDE ATOMIC-FORCE-MICROSCOPY TIPS INSCANNING TUNNELING OPTICAL MICROSCOPY - EXPERIMENTAL-STUDY

Atomic-force SiN probe tips (atomic-force microscopy) can be convenien tly used for scanning-tunneling-optical-microscopy experiments because of their transparency in the visible domain. They are known to provid e a satisfying transmission yield and spatial resolution in spite of t heir complex structural shape. Nevertheless the photon collection mech anism is not so clearly understood. We give some experimental informat ion on the conversion of the evanescent waves into a propagating mode; we show experimentally (1) that optical coupling satisfactorily obeys a classical global and macroscopic dielectric model, and (2) that the collected photons dominantly follow the photon momentum conservation rule that makes these devices directionally selective.