Non-reciprocal wave retarder based on optical rotators combination

We propose and demonstrate a method to realize an easily tunable non-reciprocal wave retarder whose phase retardation depends on the light propagation direction. The system is based on a combination of a reciprocal polarization rotator, a non-reciprocal magneto-optical rotator, and two quarter-wave plates. Experimental tests demonstrate various non-reciprocal functionalities in complete agreement with the underlying theoretical concept.