| 摘要 |
A multi-port non-reciprocal optical device with ports (12, 14, 16, 18) for receiving and emitting a light beam consisting of a first polarization and of a second polarization orthogonal to the first polarization. The device uses birefringent walk-off elements (52, 54, 56, 58), preferably birefringent crystals with optical axes oriented at 45 degrees to the axes defining the input facets of the birefringent crystal. The crystals are positioned between the ports to split the advancing light beam along a first diagonal into an ordinary beam of the first polarization and an extraordinary beam of the second polarization. Conversely, the walk-off elements combine the ordinary beam and the extraordinary beam on the reverse or return path along the diagonal to reconstruct the light beam. Paris of non-reciprocal rotation elements (72, 74, 76, 78) are placed in the paths of the ordinary and extraordinary beams to rotate the polarizations by 45 degrees and render them parallel or orthogonal, such that a polarization dependent deflecting element, e.g., a polarizing beam splitter/combiner (PSC) (102, 104) transmits or reflects both beams. The device can function as an optical circulator, isolator, attenuator or switch. Polarizers and/or free space isolators can be added to the device to increase isolation efficiency.
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