Fiber Optic Interferometry for Nanomechanical Displacement Detection

Nanoelectromechanical (NEMS) resonators with their small masses, high frequencies, and low energy dissipation, show potential for sensitive and precise applications in detecting mass, force, and other physical quantities. Optical interferometry is an important tool for NEMS. Most NEMS instruments utilize costly and hard to tune free-space design, whereas fiber optic methods have potential to be more stable, compact, and cost effective. We present an interferometer based on a fiber-optic circulator and a 635 nm laser. Having passed through the fiber, light is reflected back from the NEMS surface and from the tip of the fiber. The circulator directs reflected light to the detector, where the interference from the combination of the reflected beams occurs. Excited using an ultrasound transducer, NEMS oscillations cause oscillations of the interference signal that are recorded, for example, with a spectrum analyzer. Results of testing the interferometer are presented. Authors are thankful to Atakan B. Ari and M. Selim Hanay for providing our sample, and to Kamil Ekinci for continuous help.