AVS 59th Annual International Symposium and Exhibition
    MEMS and NEMS Tuesday Sessions
       Session MN-TuM

Paper MN-TuM5
Nanomechanical Resonator Detection using Racetrack Resonator Structures for Use in Mass Sensing

Tuesday, October 30, 2012, 9:20 am, Room 10

Session: Optomechanics and Photonic MEMS and NEMS
Presenter: V.T.K. Sauer, University of Alberta and The National Institute for Nanotechnology, Canada
Authors: V.T.K. Sauer, University of Alberta and The National Institute for Nanotechnology, Canada
Z. Diao, University of Alberta and The National Institute for Nanotechnology, Canada
M.R. Freeman, University of Alberta and The National Institute for Nanotechnology, Canada
W.K. Hiebert, University of Alberta and The National Institute for Nanotechnology, Canada
Correspondent: Click to Email
Nano-optomechanical systems have been demonstrated as an excellent mechanism for detecting the motion of nanomechanical resonators. They have very high displacement sensitivities and also very large frequency detection bandwidths. These properties make nano-optomechanical systems a promising platform for on-chip inertial mass sensing. By mass loading a resonating mechanical device, the mass of the analyte can be determined by measuring the frequency change this addition of mass causes. The high displacement sensitivities and large operational bandwidth allow for smaller mechanical resonators to be measured which allows for smaller masses to be detectable. Both cantilevers and doubly clamped beams have been detected using the interaction of the evanescent fields from photonic structures such as waveguides, ring/racetrack resonators and torroid structures. Many of these devices incorporate the mechanical resonator directly into the photonic element, but for optimal use in a mass sensing system it is preferable that any added mass not interact directly with the photonic modes. This can cause losses or other uncontrollable effects that negatively impact the operation of the mass sensor. To avoid this, the mechanical element should interact with, but still be external to, the optical cavity structure. Here, cantilever beams 0.5 to 5 μm long and doubly clamped beams 3 to 10 μm long are fabricated 70 to 170 nm from a ring resonator optical cavity. As a beam oscillates in the plane of the wafer, toward and away from a ring resonator, it modulates the ring’s effective index. This causes a phase shift in the ring which is detected by a probe laser. The beams are actuated using a power modulated pump laser which uses an optical gradient force to pull the beams toward the optical structure. To increase their mass sensitivity, the devices are implemented into a phase-locked loop and their frequency stabilities are measured.