Patent ID: 6493139
Filing Date: 2002-12-10
Classification: G02B,G02F

Abstract:
A 1Ã—2 optical switch comprising:a) a light input port having a configuration to deliver input light to a first end of a first birefringent crystal, wherein said first birefringent crystal has a structure and orientation to separate said input light into a first ordinary beam and a first extraordinary beam and cause said first ordinary beam and said first extraordinary beam to emerge from the opposite second end of said first birefringent crystal separated by a walk-off distance; and, b) a first half-wave plate and a second half-wave plate located such that said first half-wave plate intersects said first ordinary beam and said second half-wave plate intersects said first extraordinary beam, wherein said first half-wave plate has a structure and configuration so as to rotate the plane of polarization of said first ordinary beam by 45Â° and said second half-wave plate has a structure and configuration so as to rotate the plane of polarization of said first extraordinary beam by 45Â° in the opposite sense of said rotation of said first half-wave plate such that upon emerging from said first half-wave plate and said second half-wave plate said first ordinary beam and said first extraordinary beam have parallel polarizations; and, c) a variable polarization rotator located so as to intersect said first ordinary beam and said first extraordinary beam following said first and said second half-wave plates, wherein said variable polarization rotator has the capability to rotate the plane of polarization by a first rotation or a second rotation as determined by the application of an external control signal to said variable polarization rotator, wherein said first rotation and said second rotation are positive and negative 45Â°; and, d) a second birefringent crystal located so as to intersect said first ordinary beam and said first extraordinary beam at a first end thereof following said variable polarization rotator, wherein said second birefringent has a structure and orientation such that; i) said first ordinary beam and said second ordinary beam pass through said second birefringent crystal undeflected when said control signal applied to said variable polarization rotator is such as to cause said first rotation and to emerge from the opposite, second end of said second birefringent as a second ordinary beam and a second extraordinary beam; and, ii) said first ordinary beam and said second ordinary beam pass through said second birefringent crystal and emerge from the second, opposite face of said second birefringent crystal as the third ordinary beam and the third extraordinary beam, separated by said walk-off distance, when said control signal applied to said variable polarization rotator is such as to cause said second rotation; and, e) a third half-wave plate having the location to intersect said second ordinary beam and having the structure and orientation so as to rotate by 90Â° the plane of polarization of light passing therethrough; and f) a fourth half-wave plate having the location to intersect said second extraordinary beam and said third ordinary beam and having the structure and orientation to rotate by 0Â° the plane of polarization of light passing therethrough; and, g) a fifth half-wave plate having the location to intersect said third extraordinary beam and having the structure and orientation to rotate by 90Â° the plane of polarization of light passing therethrough; and, h) a third birefringent crystal located so as to intersect on a first end thereof said second and third ordinary beams and said second and third extraordinary beams following said third, fourth and fifth half-wave plates, and having the structure and orientation so as to recombine said second ordinary beam and said second extraordinary beam at a first light output port, and to recombine said third ordinary beam and said third extraordinary beam at a second light output port, wherein said first and said second light output ports are spatially separate.