The fabrication processes and simple micro-cavity size adjustment of fiber Mach-Zehnder interferometer by laser-induced micro-plasma

The article delves into the fabrication processes and micro-cavity size adjustment of fiber Mach-Zehnder interferometers (FMZIs) using laser-induced micro-plasma. It begins by introducing the various types of fiber sensors, with a particular focus on the advantages of micro-cavity-based FMZIs. The authors then present a detailed explanation of the fabrication processes, which are divided into four main stages: heat transfer, micro-plasma formation, micro-plasma expansion and ablation, and cooling down and micro-structure formation. One of the key advantages of this method is the simplicity of adjusting the micro-cavity size by merely moving the focus position, without prolonging the fabrication time. The article also includes experimental results demonstrating the high sensitivity of the fabricated FMZIs for refractive index sensing applications. Furthermore, the authors discuss the evolution of the micro-cavity geometry after each processing scan and the linear relationship between the micro-cavity size and the distance between the graphite surface and the focus plane. The article concludes by highlighting the potential for further production and practical applications of these FMZIs, despite their mechanical fragility. This comprehensive study offers valuable insights into the fabrication of high-sensitivity fiber sensors using a simplified and cost-effective method.