Optimization analysis of lateral-offset Mach-Zehnder interferometer based on no-core fiber

In this work, we thoroughly evaluate different types of lateral-offset Mach-Zehnder interferometers (MZIs) to search for the optimized design. Three different structures (SNS, SMNMS, and SNNNS. S: single-mode fiber; N: no-core fiber; M: multi-mode fiber) are proposed and their performances are compared numerically. Besides, for the SNNNS sensor, the effect of different no-core fiber (NCF) diameters on the sensor performance is discussed. The numerical analyses demonstrate that the SNNNS sensor with NCF diameter of $61.5{\mu m}$ shows the best performance among all the sensors. The experimental results confirm that, when compared with the SNS sensor, the SNNNS sensor is insensitive to the lateral-offset distance. It ensures an excellent interference performance within a large offset range, which facilitates the sensor fabrication. The optimized design of the sensor device shows the potential integration applications in the ultra-low concentration biomolecule detection field.