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

The detailed fabrication processes of fiber Mach-Zehnder interferometers (FMZIs) by nanosecond laser-induced micro-plasma and its simple micro-cavity size adjustment are proposed and demonstrated. The fabrication can be divided into 4 processes: (1) heat transfer, (2) micro-plasma formation, (3) micro-plasma expansion and ablation, (4) cooling down and micro-structure formation. The simple micro-cavity size adjustment is proposed based on the above understanding, instead of the “point processing” of femtosecond laser, here only the focus position is required to be moved. The fabricated FMZI exhibits a high sensitivity of -15,811 nm/RIU (refractive index unit) for the index sensing application.