Phase difference between the two complementary output interference signals of Fourier transform Mach-Zehnder interferometer

The partially reflected and partially transmitted light by a thin film structure or a surface or interface will have a phase difference which will be half π if the structure is non-absorbing. This paper will conduct experiments to demonstrate a method to measure this phase difference between the transmitted and reflected light in beam splitting by measuring the complementary two output signals of Fourier transform Mach-Zehnder interferometers. It will use a dielectric coated cube beam splitter and an uncoated glass surface as beam splitter respectively and it will find that there will be a nontrivial phase difference in the case of cube beam splitter. A phase difference of 0.5180(2π) was observed using a cube beam splitter while a phase difference of 0.5005(2π) was observed using a glass slab. Theoretical analysis was derived to support the experimental findings. This paper posits that this phenomenon can potentially be used as a novel way to measure the properties of thin film materials or interfaces.