Ultrahigh sensitivity stress sensing method near the exceptional point of parity-time symmetric systems

Ultralow stress sensors with ultrahigh sensitivity have an urgent need for micro-pressure measurement in aerospace, industrial automation and biomedical inventions. In this paper, a new method of ultrahigh sensitivity micro stress sensing is proposed near the exceptional point (EP) of parity-time symmetric systems theoretically. The EP is determined via the adjustment of the distance and the gain of the double ring resonators in the parity-time symmetric system, in which one ring resonator is embedded on the cantilever beam served as the sensing element. The cantilevers are characterized using finite element simulation software for their stress-deformation sensitivity by applying surface stress loads, which present a relation for the stress-deformation sensitivity of the cantilever beam. By introducing the hole in the cantilever beam, the sensitivity of the stress sensor of the structure can be improved by about 5 times compared to the cantilever beam structure without the hole. Therefore, the cantilever beam with the hole is selected as the final structure. Furthermore, compared with the single ring structure, our method enhances the sensitivity of the structure to about 8 orders of magnitude at the stress range is 0–1 nPa and the radius is 30 µm. A closed-loop feedback system is used to keep the system at the exceptional point and to reduce the readout error. This method paves a way for future design of ultrahigh sensitivity micro stress sensor, and the main benefit of this method include ultrahigh sensitivity, small size, anti-electromagnetic interference and high stability, which can be extended to more systems.