Mach–Zehnder interferometer

An optical interferometer that splits a light beam into two separate paths and recombines them. The output depends on the phase difference accumulated between the paths.

Beam splitter: An optical device that divides an incident beam into transmitted and reflected portions. The first splitter creates the two paths, and the second recombines them.
Optical phase sensing: Measurement of physical quantities by detecting changes in the phase of light. The interferometer is a standard arrangement for turning a phase shift into an intensity measurement.
Superposition principle: The rule that overlapping linear waves combine by adding their amplitudes. The fields from the two arms add at each output port.
Atom interferometer: An interferometer that splits and recombines matter waves formed by atoms. Its light-pulse sequences implement a Mach–Zehnder-like path comparison for atomic waves.
Optical phase: The phase angle specifying a light wave's position within its oscillation cycle. Different phase accumulation along the arms determines the interference at the outputs.
Electro-optic modulator: A device that changes light's phase, polarization, or amplitude using an applied electric field. Placed in one arm, it imposes a controllable phase shift for optical modulation.
Coherence: The stable phase relationship between waves that allows consistent interference. Interference remains measurable only while the two arriving fields maintain a suitable phase relationship.
Integrated photonics: The fabrication of optical components and circuits on a compact substrate. Planar waveguides can realize the two arms and couplers on a chip.
Optical path length: The distance light travels in a medium multiplied by that medium's refractive index. An arm's optical path length sets how much phase its light accumulates.
Fiber-optic gyroscope: A rotation sensor that measures the phase difference between counterpropagating light in a fiber coil. It also detects phase differences, but uses a Sagnac loop rather than separated Mach–Zehnder arms.

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