Optical circulator

Claim 2

An optical circulator having at least three ports comprising: a first birefringent plate disposed at a first port in order to separate an incident light beam at that port into two beams having orthogonal directions of polarization; a second birefringent plate disposed at a second port in order to recombine the two beams; means disposed between the plates for nonreciprocal rotation of the directions of polarization of the beams; a third birefringent plate disposed between the rotation means and the second plate for further separating the two beams; and a reflecting element disposed between the third plate and second plate for deflecting the two beams toward the second port, the said element having a slot which permits passage therethrough of an incident beam from a third port.

Claim 3

The device according to claim 1 wherein the means for nonreciprocal rotation comprises a Faraday rotator and a half-wave plate.

Claim 4

The device according to claim 1 wherein the thickness of the second plate is approximately twice the thickness of the first plate.

Claim 5

The device according to claim 1 wherein the reflecting element comprises a prism having two surfaces at ninety degrees and a third surface at forty-five degrees to the other two surfaces, and the slotted portion is formed through one of the two surfaces and the third surface.

Claim 6

The device according to claim 1 wherein the circulator includes at least four ports and further comprises: a second reflecting element with a slotted portion disposed between the first port and the first plate; and a fourth birefringent plate disposed between the reflecting element and the fourth port.

Claim 7

The device according to claim 1 wherein the birefringent plates comprise rutile, and the rotation means includes a Faraday rotator comprising an yttrium iron garnet crystal and a half-wave plate comprising quartz.

Claim 8

The device according to claim 1 wherein the birefringent plates each have optical axes in a plane at an angle of ±48 degrees with respect to the horizontal in the direction of light incident from port 1.

Claim 9

An optical circulator having at least three ports comprising: a first rectangular birefringent plate disposed at a first port and oriented in order to separate a light beam incident at that port into two beams having orthogonal directions of polarization; a second rectangular birefringent plate having a thickness greater than said first plate and disposed at a second port with an orientation so as to recombine the two beams; means disposed between the plates for nonreciprocal rotation of the directions of polarization of the beams comprising a Faraday rotator and a half-wave plate; a third rectangular birefringent plate disposed between the rotation means and the second plate and oriented in order to further separate the two beams; and a prism having two surfaces at right angles, each of which is adjacent to one of the second and third plates, and a third surface at forty-five degrees to the other two surfaces, which third surface is adjacent to a third port, said third surface and the surface adjacent to said third plate having a slotted portion formed therethrough so that the beams from the third plate are deflected by said third surface while light incident from the third port passes through the slotted portion.

Claim 10

An optical circulator having at least three ports comprising: a first rectangular birefringent plate disposed at a first port and oriented in order to separate a light beam incident at that port into two beams having orthogonal directions of polarization; a second rectangular birefringent plate having a thickness greater than said first plate and disposed at a second port with an orientation so as to recombine the two beams; means disposed between the plates for nonreciprocal rotation of the directions of polarization of the beams comprising a Faraday rotator and a half-wave plate; a third rectangular birefringent plate disposed between the rotation means and the second plate and oriented in order to further separate the two beams; and a prism having two surfaces at right angles, each of which is adjacent to one of the second and third plates, and a third surface at forty-five degrees to the other two surfaces, which third surface is adjacent to a third port, said third surface and the surface adjacent to said third plate having a slotted portion formed therethrough so that the beams from the third plate are deflected by said third surface while light incident from the third port passes through the slotted portion.