A Mach-Zehnder interferometer with two V-shaped cores for refractive index sensing

In this paper, a Mach-Zehnder interferometer (MZI) with two V-shaped cores (VCs) is proposed and the sensing characteristic of refractive index (RI) is verified theoretically and experimentally. The VCs-MZI is prepared by a novel method by using high-frequency CO2 laser polishing method and arc-discharge technology. Due to its special core deformation, a strong evanescent field in the structure is excited, which enhances the interaction between the deformed core and the external environment, resulting in high refractive index sensitivity of the structure. Meanwhile, the cladding of VCs-MZI is extruded and stacked together after arc discharge, which enhances the mechanical property of the sensor. In the experiment, Dip A (1395.6 nm) and Dip B (1427.2 nm) at the interference spectrum are selected to achieve the measurement of environmental RI and temperature. The maximum sensitivities of the Dip A and Dip B are 328.9 nm/RIU and 419.2 nm/RIU, respectively. In addition, the temperature response can be effectively decreased by calculating the relative wavelength, which is only 0.004 nm/°C in the range of 30–140 °C. Such low temperature response can be almost ignored. [Display omitted] •The proposed Mach-Zehnder interferometer (MZI) with two V-shaped cores (VCs) sensor is achieved by high-frequency CO2 laser polishing method and arc-discharge technology.•The highest refractive index sensitivity of the VCs-MZI reaches to 401.7 nm/RIU.•Low temperature response can be almost ignored.•Low cost, compact structure and easy fabrication.