Miniaturization of acoustic vector sensors enabled by viscous fluids: Towards fiber laser hair sensors

We demonstrate a path towards the miniaturization of fiber-optic acoustic sensors based on simple cantilever designs. The reduction in response due to miniaturization is offset by the introduction of a viscous fluid around the cantilever, which changes the dominant driving force and introduces damping. This dramatically changes the response and enables responses 10 times greater than otherwise expected, as well as increased operating bandwidth. We show the performance of several different cantilever sensors and the effect of different viscous fluids on their acoustic response. Theoretical modeling results show excellent agreement with our measured data.