Piezoelectric shear force detection: A geometry avoiding critical tip/tuning fork gluing

A technique for controlling the tip–sample distance in near-field optical microscopes is presented. It consists of mechanically exciting a fiber tip inserted without any adhesive between the two prongs of a high Q-piezoelectric tuning fork. The detection of the shear forces is classically achieved by measuring the decrease of the dithering amplitude when the tip approaches the surface. This simple setup greatly simplifies tip replacement and its resonance frequency tuning.