Sagnac Interferometer with Three Mirrors
This Demonstration simulates the operation of a Sagnac interferometer with three mirrors and two input beams. The interference between the output beams depends on the placement of the components. This differs from the two-mirror Sagnac interferometer in that the output beams are no longer in parallel when the mirrors are tilted.[more]
For more details about the Sagnac interferometer, refer to the Wikipedia entry for "Sagnac Effect".
To see an experimental two-mirror Sagnac-loop, see R.-B. Jin, et al., "Pulsed Sagnac Polarization-Entangled Photon Source with a PPKTP Crystal at Telecom Wavelength." arxiv.org/abs/1311.3462.
To see an experimental three-mirror Sagnac-loop, see T. Nagata, et al., "Beating the Standard Quantum Limit with Four Entangled Photons." arxiv.org/abs/0708.1385.