Observation of non-trivial phase difference between the two complementary output interference waves in Mach-Zehnder interferometer

Fourier transform spectrometers with Mach-Zehnder interferometer designs will have two interference signal outputs. Ideally the two output interference wave signals should have exactly opposite sign due to the principle of conservation of energy under the assumption of ideal lossless beam splitter. This paper will conduct an experiment to measure this phase difference between the balanced and unbalanced Fourier transform interferometer outputs of a helium neon laser light by a dielectric coated cube beam splitter and an uncoated glass surface. It was found that there is nontrivial phase difference by the cube beam splitter. We think that this phenomenon can be potentially useful as a novel way to study the properties thin film structures.