The Mach-Zehnder Interferometer (MZI) is a device which, having as an input a light source, it splits it in two parts and it recombines them to analyze if a constructive/destructive interference occurs.
The MZI is mainly done by using two 50-50 splitters (one operating as a splitter and one as a combiner) and two optical waveguide paths.
To achive the split of light, we can use a Y-Branch: it takes as imput the light source (described by the intensity \(I_i\) and the electric field \(E_i\)) and it split it in two portions having intensity \(I_{1,2}=I_i\)/2 and electric field \(E_{1,2}=E_i\)/\(\sqrt{2}\)