All-fiber microcantilever sensor monitored by a low-cost fiber-to-tip structure with subnanometer resolution

We demonstrate a low-cost, high-sensitivity, all-fiber microcantilever sensor, a fiber-to-tip microcantilever sensor (FTMS). In this sensor, a nanosize fiber tip serves as both microcantilever and miniaturized light probe. Subnanometer displacements of the fiber-tip cantilever are expected to be registered by measuring the light intensity that it receives from a collinearly aligned single-mode fiber (SMF). We found that the cantilever-displacement curve is defined by the Gaussian profile of the fundamental mode, HE(11), guided in the aligned SMF. An FTMS vibration sensor has been implemented as an example of the technique, exhibiting an estimated resolution of 2 A. The FTMS should open new ways of inexpensive fiber-optic microcantilever sensing.