Ultrasensitive fiber tilt sensor based on a mobile inscribed microbubble along the arc-shaped inwall of the...

We report a novel fiber tilt sensor based on a mobile microbubble inscribed in an ellipsoidal liquid-filled microcavity. When the tilt angle changes, the microbubble in the liquid can drift along the upper arc-shaped inwall of the microcavity and stay at a vertex to get a state of mechanical equilibrium. The drifting microbubble induces a drastic change on the optical path difference between the light beams in the microcavity and, consequently, on the reflection spectrum, which makes it a tilt angle sensitive element. The experimental results show that the tilt angle sensitivity is as high as 160.21 nm/deg, and the detection resolution of such a sensor can reach up to 2.3×10^-3  deg. Moreover, such a fiber tilt sensor is capable of distinguishing the tilt direction, since the movement of the microbubble is tilt direction dependent.