Abstract: To provide a magneto-optic optical device, such as a variable optical attenuator, an optical modulator or an optical switch, that is small, has a low power consumption and has high speed. The above object is achieved by a magneto-optic optical device characterized by comprising at least one magneto-optical crystal, a magnetic field application mechanism for applying to the magneto-optical crystal a magnetic field component in a direction vertical to a light entrance/exit plane, and at least one electromagnet for changing a position where the magnetic field component applied to the magneto-optical crystal becomes zero.

Abstract: A Faraday rotator and an optical attenuator using the Faraday rotator in which both a fixed magnetic field parallel to and a valuable magnetic field perpendicular to the optical axis are applied to Faraday elements, said optical axis being in the <111> direction of single crystal of garnet, characterized in that three single crystals of garnet of substantially the same thickness having the Faraday effect are used to form Faraday elements and the Faraday elements are arranged in such a manner that a variable magnetic field is applied to one of the Faraday elements, over a range extending 5 deg. each to the left and right of the line connecting the (111) plane in the center of the stereographic projection chart with the (−1−12) plane on the outermost circumference or a plane equivalent thereto in the chart, whereas a variable magnetic field is applied to the remaining two elements, over a range extending 5 deg.

Abstract: There is provided a magneto-optic optical device, such as a variable optical attenuator, an optical modulator or an optical switch, which is small, has a low power consumption, and has a high speed. A magnetic field in the same direction as the traveling direction of a light beam is applied vertically to a light entrance/exit plane of a Faraday rotator by a permanent magnet, and a light transmission region is completely contained in, for example, a region of a magnetic domain A, and emits a light beam without attenuation. When power is applied to an electromagnet to cause a region of the magnetic domain A and a region of a magnetic domain B to substantially equally exist in the light transmission region, a Faraday rotation angle &thgr;f becomes 0°. When a further large current is made to flow to the electromagnet, the light transmission region is completely contained in the region of the magnetic domain B.

Abstract: An optical element comprises a Faraday rotator and first, second, third, and fourth birefringent regions. The first and second regions and a fifth region are joined to one plane of the rotator. The third and fourth regions and a sixth region are joined to the opposite place of the rotator. Light that has passed through the first region passes through the third region. Light that has passed through the second region passes through the fourth region. The optical axes of the first and second regions intersect orthogonally. The optical axes of the third and fourth regions intersect orthogonally. The principal planes of the first and second regions have the same ground surfaces. The principal planes of the third and fourth regions have the same ground surfaces. The first through fourth regions are of the same material. At most 10% of the light beam travels through the fifth and sixth regions.

Abstract: A Faraday rotator and an optical attenuator using the Faraday rotator in which both a fixed magnetic field parallel to and a valuable magnetic field perpendicular to the optical axis are applied to Faraday elements, said optical axis being in the <111> direction of single crystal of garnet, characterized in that three single crystals of garnet of substantially the same thickness having the Faraday effect are used to form Faraday elements and the Faraday elements are arranged in such a manner that a variable magnetic field is applied to one of the Faraday elements, over a range extending 5 deg. each to the left and right of the line connecting the (111) plane in the center of the stereographic projection chart with the (−1−12) plane on the outermost circumference or a plane equivalent thereto in the chart, whereas a variable magnetic field is applied to the remaining two elements, over a range extending 5 deg.

Abstract: A composite optical element comprises a first optical material and a second optical material joined to one plane of a third optical material. The first and second optical materials are of equal thickness and having ground surfaces flush with each other on both of their principal planes. The first and second optical materials are fixedly joined to one another, and one of the principal planes of the two materials is ground. Then, the ground principal plane of the first and second optical materials is joined to the third optical material. Then, the other principal plane of the first and second optical materials is ground. A preferred embodiment is an optical isolator wherein the first and second optical materials are birefringent materials and are joined to one side of a Faraday rotator having a Faraday rotational angle of approximately 45°, and third and fourth birefringent materials are similarly joined to the other side of the rotator.

Abstract: An object is to provide a magnetic garnet material, even if a thickness of an element is made thin, in which a sufficient Faraday rotation capacity can be obtained, a magnetic field for saturation can be controlled to be less than 200 (Oe), and a magnetic compensation temperature can be controlled to be less than 0° C. as well as to provide a Faraday rotator which can be made thin, suppresses a manufacturing cost and achieves a high yielding. The above object can be achieved by a magnetic garnet material known as the general chemical formula BixYbyGdzM13-x-y-zFewM2uM35-w-uO12 and the Faraday rotator using the above material. However, M1 is more than one kind of chemical elements which can replace Bi, Yb or Gd, M2 is more than one kind of non-magnetic chemical elements which can replace Fe, and M3 is more than one kind of chemical elements which can replace Fe and M2. Further, x, y, z, w and u respectively satisfies 1.0≦x≦1.6, 0.3≦y≦0.7, 0.9≦z≦1.6, 4.0≦w≦4.3 and 0.7≦u≦1.0.

Abstract: A composite optical element comprising a Faraday rotator, a first and a second birefringent regions, and a fifth region, all said three regions being joined to one plane of said rotator, and a third and a fourth birefringent regions, and a six region, all said three regions being joined to the opposite plane of said rotator,

Abstract: A composite optical element comprises a first optical material and a second optical material joined to one plane of a third optical material. The first and second optical materials are of equal thickness and having ground surfaces flush with each other on both of their principal planes.The first and second optical materials are fixedly joined to one another, and one of the principal planes of the two materials is ground. Then, the ground principal plane of the first and second optical materials is joined to the third optical material. Then, the other principal plane of the first and second optical materials is ground.A preferred embodiment is an optical isolator wherein the first and second optical materials are birefringent materials and are joined to one side of a Faraday rotator having a Faraday rotational angle of approximately 45.degree. and third and fourth birefringent materials are similarly joined to the other side of the rotator.

Abstract: An optical fiber terminal provided with an optical isolator having a Faraday rotator, including an optical fiber retained in a ferrule, an optical isolator element, and a permanent magnet for applying a magnetic field to the Faraday rotator is improved to provide a minimum possible outer diameter. The fiber terminal comprises an attaching member for fixedly attaching the optical isolator and the permanent magnet to the ferrule together; an air layer between an end of said optical fiber and said optical isolator element; a first outer diameter of said ferrule on the side of the optical isolator constituting a maximum diameter of the optical fiber terminal, a second outer diameter of said ferrule on the side of the optical fiber being smaller than the first maximum diameter; and the periphery of the permanent magnet being exposed to the air.

Abstract: In an optical isolator including first and second birefringent plates whose optical axes are angularly different and a Faraday rotator inserted therebetween having a Faraday rotation angle of .theta..sub.f, (1) the angles of the optical axes of the first and second birefringent plates are so set that a forward incident polarized light passes through the first and second birefringent plates both as ordinary lights or both as extraordinary lights, and the relationship .theta..sub.f +.phi..sub.eff =90.degree. is satisfied when an actually used incident polarized light is incident in an oblique direction, or (2) the angles of the optical axes of the first and second birefringent plates are so set that a forward incident polarized light passes through one of the first and second birefringent plates as an ordinary light and the other birefringent plate as an extraordinary light, and the relationship .theta..sub.f -.phi..sub.eff =0.degree. is satisfied.

Abstract: A Faraday rotator which comprises, in combination, a garnet material of an atomic ratio compositionBi.sub.x P.sub.y Q.sub.3-x-y Fe.sub.5-w M.sub.w O.sub.12in which P is one or more elements chosen from among Y, La, Sm, Eu, Tm, Yb, and Lu, Q is one or more elements chosen from among Gd, Tb, Dy, Ho, and Er, M is one or more nonmagnetic elements that can substitute for Fe, and 0.7.ltoreq.x.ltoreq.2.0, 0.5.ltoreq.y.ltoreq.2.3, 0.ltoreq.3-x-y.ltoreq.1, and 0..ltoreq.w.ltoreq.1.0, and a magnet for applying a magnetic field smaller than the saturation magnetic field to said material. Preferably, the value w ranges from 0.2 to 0.7, and a Faraday rotator especially excellent is one using a garnet material in which M.sub.w is represented by A.sub.k D.sub.l where A is an element to be substituted for the site a of the garnet, selected, e.g., from among Sc, In, etc., D is an element to be substituted for the site d of the garnet, selected, e.g., from among Ga, Al etc., and 0.ltoreq.k<0.1, 0.2.ltoreq.l.ltoreq.0.

Abstract: A magneto-optic element is employed to create an optical attenuator, an optical modulator and a magnetic field strength sensor. The magneto-optic element exhibits a multiple domain structure in a state where no magnetic field is applied, wherein magnetization components in adjacent domains of the element along a direction in which a light beam travels are different from one another. The optical attenuator further includes apparatus for applying a magnetic field of variable strength to the magneto-optic element. The optical modulator further includes apparatus for applying a modulated magnetic field to the magneto-optic element. The magnetic field strength sensor operates by placing the magneto-optic element in the vicinity of an object to be measured. A light beam is directed from an input optical fiber onto the magneto-optic element and the element diffracts the light beam. A portion of the light beam exiting the element impinges on a reflector and is received by a second optical fiber.

Abstract: An optical fiber terminal fitted with an optical isolator in close proximity in a unitary structure comprises an optical fiber, a ferrule which holds the optical fiber in position, at least one magneto-optical element located as aligned with the optical fiber, and a cylindrical permanent magnet that applies a magnetic field to the magneto-optical element. The magneto-optical element is disposed axially outside of the magnet, and the end face of the optical fiber is located in the hollow of the magnet or in the space between the magnet and the magneto-optical element, so that the overall outside diameter and length can be decreased. The ferrule, made of a soft magnetic material, increases the magnetic field strength of the magnet.

Abstract: An optical isolator having no dependence on direction of plane of polarization is provided by using a pair of polarization splitters, each comprising at least two parallel optical waveguides, and a birefringent crystal plate inserted in a groove formed obliquely in said waveguides. A plane formed by said two optical waveguides is parallel to vector normal to the incident surface of said birefringent crystal plate, the optical axis of said birefringent crystal plate is also parallel to said plane, and the following relationship is substantially satisfied:tan .theta..sub.in =A/[.sqroot.B(n.sub.in -.sqroot.B)]whereA=(n.sub.O.sup.2 -n.sub.E.sup.2) cos .theta..sub.C sin .theta..sub.CB=n.sub.E.sup.2 sin.sup.2 .theta..sub.C +n.sub.O.sup.2 cos .theta..sub.Cn.sub.in : Refractive index of the optical waveguidesn.sub.O : Refractive index of the birefringent crystal plate for ordinary lightn.sub.E : Refractive index of the birefringent plate for extraordinary light.theta..sub.

Abstract: A magneto-optic element is employed to create an optical attenuator and an optical modulator. The magneto-optic element exhibits a multiple domain structure in a state where no magnetic field is applied, wherein magnetization components in adjacent domains of the element along a direction in which a light beam travels are different from one another. The optical attenuator further includes apparatus for applying a magnetic field of variable strength to the magneto-optic element. The optical modulator further includes apparatus for applying a modulated magnetic field to the magneto-optic element. In both devices, a light beam is directed from an input optical fiber onto the magneto-optic element. The element diffracts the light beam. A portion of the light beam exiting the element impinges on a reflector and is received by a second optical fiber. In the optical attenuator, that portion of light is attenuated with respect to the light in the input optical fiber.

Abstract: An optical fiber terminal fitted with an optical isolator comprises an optical fiber, a ferrule which holds the optical fiber in position, and an optical isolator which includes an optical isolator assembly having at least one magneto-optical element and at least one polarizer and means for applying a magnetic field of less than saturation to the magneto-optical element. The fiber, ferrule, and isolator are disposed close to one another and joined integrally. The optical isolator has a maximum outside diameter not more than twice, preferably substantially equal to, the outside diameter of the ferrule.

Abstract: A polarizer and a method of manufacturing the polarizer comprising first zones which are formed by one or more layers and second zones which are formed by one or more layers, the zones being alternately and horizontally arranged on a common plane. A material of at least one layer of at least either zones is birefringent, and the birefringent layer is formed by oblique vapor deposition. The polarizer, excellently suited for quantity production and for space and size reduction, can be formed directly and simply on the planes of light beam incidence or emergence of various optical elements. The invention also concerns polarizer-equipped optical elements and a method of manufacturing such elements which have the polarizer directly formed by oblique deposition on the plane of light beam incidence, emergence, or reflection of the optical elements.