Detection of displacements in the nanometre range by optical tunnelling

Abstract Our concern is the exploitation of the so-called optical tunnelling effect to detect the cantilever deflection in atomic force microscopy (AFM) caused by the interatomic forces established between a sample surface and the force sensor. Towards this end, we have developed a displacement sensor based on the phenomenon of evanescent wave coupling or the optical tunnelling effect. Furthermore, we have implemented a computer programme simulating a planar model of a three media system (optical tip, gap and waveguide where total internal reflection occurs). The proposed method is particularly suitable for biophysical applications of AFM.