title: Silicon nanowires: where mechanics and optics meet at the nanoscale.
abstract: Mechanical transducers based on nanowires promise revolutionary advances in biological sensing and force microscopy/spectroscopy. A crucial step is the development of simple and non-invasive techniques able to detect displacements with subpicometer sensitivity per unit bandwidth. Here, we design suspended tapered silicon nanowires supporting a range of optical resonances that confine and efficiently scatter light in the visible range. Then, we develop an optical method for efficiently coupling the evanescent field to the regular interference pattern generated by an incoming laser beam and the reflected beam from the substrate underneath the nanowire. This optomechanical coupling is here applied to measure the displacement of 50 nm wide nanowires with sensitivity on the verge of 1 fm/Hz(1/2) at room temperature with a simple laser interferometry set-up. This method opens the door to the measurement of the Brownian motion of ultrashort nanowires for the detection of single biomolecular recognition events in liquids, and single molecule spectroscopy in vacuum.
authors.affiliation: Instituto de Microlectrónica de Madrid, CSIC, Isaac Newton 8 (PTM), Tres Cantos, Madrid 28760, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ramos
authors.forename: Eduardo
authors.initials: E
authors.lastname: Gil-Santos
authors.forename: Oscar
authors.initials: O
authors.lastname: Malvar
authors.forename: Jose M
authors.initials: JM
authors.lastname: Llorens
authors.forename: Valerio
authors.initials: V
authors.lastname: Pini
authors.forename: Alvaro
authors.initials: A
authors.lastname: San Paulo
authors.forename: Montserrat
authors.initials: M
authors.lastname: Calleja
authors.forename: Javier
authors.initials: J
authors.lastname: Tamayo