The Mach-Zehnder interferometer is a device used to determine the relative phase shift between two collimated beams from a coherentlight source. The flexibility in fringe localization gives Mach-Zehnder interferometer one of the important advantage over other interferometers.

Refractive index of air can be measured very accurately with this interferometry setup. Special cell is constructed for filling the air. Test cell is placed in one of its optical arms of the interferometer. No other factors such as convective airflow should be present which can generate optical path differences.

The device is assembled using modular building blocks on a rigid base. A honeycomb anti-vibration breadboard of size 800 mm x 600 mm is supplied as the base. Mirrors, beam splitter and diode laser along with their mounts are supplied as modular building blocks.Interferometer is built by assembling the building blocks on the breadboard as per the desired optical layout. Optics and laser head are held using kinematic mounts with two axes fine adjustment facility. Precision alignments for obtaining the interference fringes are done using kinematic mounts.