Butt coupled microcantilever in sensing applications
K. Zinoviev, J. A. Plaza, V. Cadarso, L. M. Lechuga and C. Domínguez
SPIE Photonics Europe, 6186, 2006, 618607 - DOI: 10.1117/12.662393
Abstract: Butt coupled optical waveguides are well known in integrated optics by high sensitivity of energy transfer to their misalignment with respect to each other. This might be detrimental if efficient and firm coupling from one light guide to another is needed, for example, coupling from a fiber to a waveguide on chip. However, this phenomena is efficiently used for sensing applications, where small misalignment between two objects provided with the waveguides can be detected. In this work we studied the abilities of this method to detection of ultrasmall displacements of microcantilevers frequently used in biological research. In the proposed design the cantilever itself acts as a waveguide operated in visible range. The simulations demonstrated ability to detect cantilever deflections with sensitivity of 18 fm/Hz1/2. The capability of detection with subangstrom resolution in the dynamic mode was demonstrated experimentally in air. The preliminary experiments in liquids are presented. The technique can be considered as an alternative to the known methods used for read-out of response of microcantilevers to external nanomechanical forces exerted on them.