Abstract
An accelerometer utilising the optomechanical coupling between an optical whispering gallery mode (WGM) resonance and the motion of the WGM cavity itself was prototyped and field-tested on a vehicle. We describe the assembly of this portable, battery operated sensor and the field-programmable gate array automation. Pre-trial testing using an electrodynamic shaker demonstrated linear scale-factors with <0.3% standard deviation ( g range where g = 9.81 ms), and a strong normalised cross-correlation coefficient (NCCC) of r when compared with an integrated circuit piezoelectric (ICP) accelerometer. A noise density of 40 g Hz was obtained for frequencies of 2–7 kHz, increasing to 130 g Hz at 200 Hz, and 250 g Hz at 100 Hz. A reduction in the cross-correlation was found during the trial, r = 0.36, which we attribute to thermal fluctuations, mounting differences, and the noisy vehicle environment. The deployment of this hand-fabricated sensor, shown to operate and survive during ±60 g shocks, demonstrates important steps towards the development of a chip-scale device.
Highlights
Measurements of motion, vibration, and shock are universally required for a wide range of applications such as inertial navigation, and structural monitoring for infrastructure, health and machining [1]
On the other hand, benefit from large single-photon optomechanical coupling strengths resulting in measurable shifts and linewidth broadening of the cavity resonance, even, in some cases, when the mechanical oscillator is displaced by its zero point motion [11]
We previously demonstrated an optomechanical accelerometer that uses optical whispering gallery mode (WGM) to detect the motion of the optical cavity itself, reaching a noise density of 4.5 μg Hz−1/2 in the laboratory [7]
Summary
Measurements of motion, vibration, and shock are universally required for a wide range of applications such as inertial navigation, and structural monitoring for infrastructure, health and machining [1]. On the other hand, benefit from large single-photon optomechanical coupling strengths resulting in measurable shifts and linewidth broadening of the cavity resonance, even, in some cases, when the mechanical oscillator is displaced by its zero point motion [11]. Owing to their small size, ease of integration with industry standard components and known routes towards chip-scale fabrication [12], these sensors offer attractive commercial opportunities. For the first time, that the tapered waveguide can survive shocks of ±60 g, which would be of interest for many WGM [5,7,13,17,18,19,20,21,22] and photonic crystal experiments [6]
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