Abstract

Increasing the sensitivity and miniaturizing the size of liquid-level sensors are crucial for confined installation space. Here we propose and demonstrate a highly sensitive liquid-level sensor based on a compact optical reflective microfiber probe. By tracking the resonant wavelength shift of the in-line Mach–Zehnder interferometer generated between the $ {\rm HE}_{11} $ and $ {\rm HE}_{12} $ modes, liquid-level sensing can be realized. Through optimizing the structure parameters of the microfiber probe, an ultra-high sensitivity of $\sim{367.644}\;{\rm nm/mm}$ is achieved in experiment, which is two to three orders of magnitude higher than other reported liquid-level sensors, to the best of our knowledge. Considering the high sensitivity and compact structure of the sensor, it has great potential in real-time intelligent monitoring of tiny changes in the liquid level such as small autonomous drones and micro-channels.

© 2019 Optical Society of America

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