Force Detection Using a Fiber-Optic Cantilever

A force measurement technique has been developed that utilizes a clamped fiber optic element both as a cantilever and as a highly sensitive probe of the static and dynamic displacement of a sample that is mounted near its free end. Light from a 1.5 mW superluminescent diode coupled into the fiber is used to detect displacement with 610/sup -13 mHz/sup -1/2 sensitivity for frequencies above 40 kHz. This technique has been used to study the interaction between macroscopic bodies with atomic sensitivity. Here, we report measurements of stiffness of junctions that form when two gold surfaces are brought into contact.