| AVS 63rd International Symposium & Exhibition | |
| MEMS and NEMS | Wednesday Sessions |
| Session MN+NS-WeA |
| Session: | Optomechanics, Photonics, and Quantum Nanosystems |
| Presenter: | Thomas Michels, Ilmenau University of Technology, Germany |
| Authors: | T. Michels, Ilmenau University of Technology, Germany B.R. Ilic, National Institute of Standards and Technology V. Aksyuk, National Institute of Standards and Technology I.W. Rangelow, Ilmenau University of Technology, Germany |
| Correspondent: | Click to Email |
Research and development of transducers based on cavity optomechanics is a topic of high interest particularly because these transducers enable measurement of mechanical motion down to the fundamental limit of precision imposed by quantum mechanics. We have developed an on-chip cavity optomechanical transducer array that combines high bandwidth and high sensitivity with compactness, robustness, small size, and potential for low cost batch fabrication inherent in MEMS. The parallelization of multiple probes within one transducer array allows the simultaneous measurement of serial forces or mass detection.
Our fully-integrated, fiber-pigtailed transducer array combine high sensitivity (≈ 0.5 fm Hz-1/2 to ≈ 10 fm Hz-1/2), high bandwidth optomechanical readout and built-in thermal actuation. We use a wafer-scale microfabrication process combining one e-beam patterning, six stepper, and three contact mask aligner lithography steps. These define the silicon nitride (SiN) cantilever, the single-crystal silicon-on-insulator (SOI) microdisk optical cavity with high optical Q (up to 2x106), SOI optical waveguides, and the patterned gold layer for bimorph actuation. Back and front side anisotropic potassium hydroxide (KOH) silicon etch allows to overhang the cantilever over the edge of the silicon chip and to define v-grooves for single mode optical fiber attachment. Two sacrificial silicon dioxide layers are removed by an isotropic hydrofluoric acid (HF) etch to free the mechanically movable structures.
The SiN cantilever can be excited by an electrical signal supplied to an integrated thermal actuator. The cantilever is evanescently coupled to a high-Q optical whispering gallery mode of the optical microdisk cavity and the motion is detected by measuring the resonance frequency shift of the optical cavity mode. The actuator can be used to individually address the cantilever and dynamically move them as well as to tune the distance between the cantilever and the optical cavity, to change the sensitivity and range of measurement of the cantilever. One side of the cantilever overhangs the edge of the chip, where it can be easily coupled to a variety of off-chip samples and physical systems of interest. A 10 um long probe is currently designed to have a stiffness of 0.1 N/m to 5 N/m and a resonance frequency of 50 kHz to 2 MHz, while the design can be easily and broadly tailored for specific sensing applications.