Micro-optical vibrometer/accelerometer using dielectric microspheres

In this paper, an optical vibrometer/accelerometer is designed using micro-optical dielectric sensors based on whispering gallery modes (WGM) phenomena. The proposed design is created as a sphere made from polydimethylsiloxane (PDMS). The dielectric sensor would be laid between a piezo stack and a proof mass of 10^-4  kg (implemented as body force to the sensor) in the vertical position. Once the piezo stack starts to impose a vibration in the vertical direction, the proof mass starts to vibrate, leading to a change in the morphology of the sensor. In turn, the WGM shifts would be seen on the transmission spectrum and would be related to the vibration/acceleration of the piezo stack. An analysis based on the force transmissibility from the piezo stack to the optical sensor and calibrations are carried out along with preliminary designs and experiments. Results showed that the proposed sensor could reach a very high resolution up to 8 nano-g with sensitivity dλ/da≈2.33  pm/μg.