Abstract: This invention is related to method for assembling an optical attenuator to attenuate an optical beam. The method includes a step of a) collimating the optical beam from an input optical waveguide into a substantially collimated beam comprising an upper segmented-portion and a lower segmented-portion. The method further includes steps of b) transmitting the collimated onto a phase shifting means comprising at least an upper phase shifting means for generating a phase difference between the upper segmented-portion and the lower segmented-portion and c) generating a self-interference between the upper segmented-portion and the lower segmented-portion of the collimated beam and focusing the collimated beam into an output optical waveguide with an attenuation resulting from the self-interference.

Abstract: An optical signal transmission system equipped with a magneto-optical modulator is provided. The magneto-optical modulator works to modulate an optical beam emitted from a light source and consists of a polarizer, a magneto-optical element, an analyzer, a dc field generator, a high-frequency field generator, and an impedance adjuster. The dc field generator works to apply a dc bias field to the magneto-optical element. The high-frequency generator is responsive to the high-frequency signal from said high-frequency signal generator to apply a high-frequency field to the magneto-optical element. The impedance adjuster works to adjust impedance of the high-frequency field generator for establishing effective transmission of the high-frequency signal to the high-frequency field generator, thereby increasing a modulation range up to frequencies higher than an upper limit of typical magneto-optical modulators.

Abstract: An optical data apparatus has a first polarization splitter configured to receive an input and split the input into first and second orthogonal polarizations. A second polarization splitter is included and configured to combine the first and second orthogonal polarizations. A non-reciprocal phase rotator is positioned between the first and second polarization splitters. At least one birefringent crystal is positioned between the first and second polarization splitters to create wavelength dependent bi-directionality.

Abstract: An optical filter having a changeable optical transmittance versus wavelength characteristic curve to variably filter a light. The curve maintains a fixed optical transmittance at a specific wavelength as the curve is changed. The optical filter includes a Faraday rotator having a variable Faraday rotation angle, to change the optical transmittance versus wavelength characteristic curve.

Abstract: An optical isolator comprsing at least two parts of a Faraday rotator obtained from a garnet crystal and an analyzer, which is small in size, can be mounted directly to a semiconductor laser. The garnet crystal is grown, by a liquid-phase epitaxial growth technique, on the substrate of a garnet with a lattice constant of 12.514±0.015 Å, and consists of the following composition formula: (Tb1−(a+b+c+d)LnaBibM1cEud)3(Fe1−eM2e)5O12 where Ln is an element selected from rare-earth elements excluding Tb and Eu, and Y; M1 is an element selected from elements Ca, Mg, and Sr; M2 is an element selected from elements of Al, Ga, Sc, In, Ti, Si, and Ge; a, b, c, d, and e are defined as 0≦a≦0.5, 0.3<b≦0.6, 0≦c≦0.02, 0<d≦0.3, and 0.01<e≦0.3, respectively.

Abstract: A low-rate data transmission system and method are disclosed that use the Faraday effect to modulate the polarization state of light traveling in an optical fiber. The resulting change in polarization is used to communicate information over the fiber. The low-rate data transmission system includes a low-rate signal source producing current in a wire coil wrapped around an optical fiber. Information is conveyed in accordance with the present invention by the selectively introducing a polarization change into the light carried by the fiber. Generally, the source light at the input of the optical fiber can be randomly polarized and information is conveyed in accordance with the present invention by the presence or absence of a predefined polarization introduced into the light. The longitudinal magnetic field produced by a current in the coil rotates the plane of polarization of the light, in accordance with the well-known Faraday effect.

Abstract: Described are the design of a rare earth iron garnet sensor element, optical methods of interrogating the sensor element, methods of coupling the optical sensor element to a waveguide, and an optical and electrical processing system for monitoring the polarization rotation of a linearly polarized wavefront undergoing external modulation due to magnetic field or electrical current fluctuation. The sensor element uses the Faraday effect, an intrinsic property of certain rare-earth iron garnet materials, to rotate the polarization state of light in the presence of a magnetic field. The sensor element may be coated with a thin-film mirror to effectively double the optical path length, providing twice the sensitivity for a given field strength or temperature change. A semiconductor sensor system using a rare earth iron garnet sensor element is described.

Abstract: Optical isolators for use in fiber optic networks utilizing a birefringent wedge set with a Faraday rotator disposed between the birefringent wedges. In a first embodiment a polarization maintaining optical isolator is disclosed which will maintain the polarization of the light which passes through it in a forward direction and block light in the reverse direction. In a second embodiment a single polarization optical isolator is disclosed which will pass only a single linear polarization of the light in a forward direction and block any light in the reverse direction.

Abstract: An optical isolator having a constitution in which a Faraday rotator is sandwiched by two polarizers, which can be more easily produced at a reduced cost. An optical isolator is constituted so that it comprises the following constituent elements in the described order: a first reflection-type polarizer made of a polymeric multilayer film; a Faraday rotator capable of rotating the polarizing. plane by 45 degrees; a tapered glass plate; and a second reflection-type polarizer made of a polymeric multi-layer film.

Abstract: There is provided a Faraday rotation angle varying device in which external magnetic fields are applied from at least two directions to a garnet single crystal having a Faraday effect and a synthesized magnetic field is varied so that Faraday rotation angle of light which transmits through the garnet single crystal is controlled. The device has a base film of garnet single crystal having a rotation angle varied in accordance with variation of a synthesized magnetic field, and a compensating film of a garnet single crystal having a constant Faraday rotation angle. The base film has a wavelength coefficient sign and the compensating film has a wavelength coefficient sign which is different from that of the base film, so that a wavelength variation component of the Faraday rotation angle of the base film is reduced by the compensating film. For example, a fixed magnetic field parallel to a light direction is applied by permanent magnets and a variable magnetic field is applied by an electromagnet.

Abstract: Method for optical energy transfer and energy guidance uses an electric field to control energy propagation using a class of poled structures in solid material. The poled structures, which may form gratings in thin film or bulk configurations, may be combined with waveguide structures. Electric fields are applied to the poled structures to control routing of optical energy. Techniques include frequency-selective switchable- and adjustable-tunable reflection, splitting, directional coupling, frequency-tunable switching and efficient beam combining, as well as polarized beam combining. Adjustable tunability is obtained by a poled structure which produces a spatial gradient in a variable index of refraction along an axis in the presence of a variable electric field. In one embodiment, the present invention is a method of switching a grating which consists of a poled material with an alternating domain structure of specific period.

Abstract: An object of the invention is to provide a small size Faraday rotator which is easy to produce and enables reliable reduction of temperature dependence of the Faraday rotation angle, by defining the crystal orientation and arrangement order of each Faraday element when three or more Faraday elements are used. For this purpose, a Faraday rotator of the present invention comprises: a Faraday element section being composed of a plurality of Faraday elements, a permanent magnet for applying a magnetic field to each Faraday element in a parallel direction to an optical axis direction, and an electromagnet for applying a variable magnetic field in a perpendicular direction to the optical axis direction, wherein each Faraday element is arranged such that the crystal orientation of each is perpendicular to a light beam direction, and crystal orientations of adjacent Faraday elements are opposed to each other.

Abstract: The present invention aims at providing a variable optical attenuator to achieve the reduction of the wavelength-dependency of the entire device, by optimizing the magneto-optical system of the variable optical attenuator by deliberating the wavelength-dependency of Faraday rotation angles. To this end, the variable optical attenuator according to the present invention comprises: a Faraday rotator for providing a variable Faraday rotation angle; and a polarizer and an analyzer arranged in front of and behind the Faraday rotator, respectively, wherein the angle formed between the optical axis of the analyzer and the optical axis of the polarizer is set such that the Faraday rotation angle at which the wavelength-dependency of the optical attenuation amount of the variable optical attenuator becomes the maximum, is brought to be substantially 0°, to thereby reduce the wavelength-dependency of the optical attenuation amount at the aforementioned Faraday rotation angle.

Abstract: An optical signal transmission system equipped with a magneto-optical modulator is provided. The magneto-optical modulator works to modulate an optical beam emitted from a light source and consists of a polarizer, a magneto-optical element, an analyzer, a dc field generator, a high-frequency field generator, and an impedance adjuster. The dc field generator works to apply a dc bias field to the magneto-optical element. The high-frequency generator is responsive to the high-frequency signal from said high-frequency signal generator to apply a high-frequency field to the magneto-optical element. The impedance adjuster works to adjust impedance of the high-frequency field generator for establishing effective transmission of the high-frequency signal to the high-frequency field generator, thereby increasing a modulation range up to frequencies higher than an upper limit of typical magneto-optical modulators.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: An optical attenuation device to attenuate the intensity of incident light, comprising an optical attenuation unit including at least two different type magneto-optical optical attenuation elements coupled in a cascade together.

Abstract: An integrated micro-optical system includes at least two wafers with at least two optical elements provided on respective surfaces of the at least two wafers. An active element having a characteristic which changes in response to an applied field may be integrated on a bottom surface of the wafers. The resulting optical system may present a high numerical aperture. Preferably, one of the optical elements is a refractive element formed in a material having a high index of refraction.

Abstract: The present invention relates to a tunable optical filter having a variable wavelength characteristic of transmittance. The tunable optical filter includes first and second polarizers each having a transmission axis determining a polarization axis of transmitted polarized light, a birefringent element having an optic axis determining a phase difference given between two orthogonal components of transmitted polarized light, and a Faraday rotator for giving a variable Faraday rotation angle to transmitted polarized light. The birefringent element and the Faraday rotator are provided between the first and second polarizers.

Abstract: In all-optical networks, high speed optical switching and routing becomes one of the most important issues for interconnecting the transport network layers. This invention describes novel polarization-independent high speed optical switches using a digital Faraday rotator, which can also be used for various other optical switching devices. The basic digital Faraday rotator device is composed of (a) a semi-hard or hard iron garnet based magneto-optic crystal having bi-stable magnetization states at zero external magnetic field. (b) a wire winding around the crystal for changing the magnetization states by pulsed current having both fast rise time and short duration. (c) a circuit generating the required current pulses with both polarities.

Abstract: A light wavelength converting element having a periodic polarization inversion structure is produced in the following manner: a comb-shaped electrode and a plate electrode are attached to both surfaces of an MgO-LN substrate, and the MgO-LN substrate is immersed in an insulating liquid. In a state in which substrate temperature is at room temperature, the plate electrode is grounded and a pulse voltage of +0.75 kV, for example, is applied for one second such that the comb-shaped electrode has positive potential. Then, the comb-shaped electrode is grounded and a pulse voltage of −3.25 kV, for example, is applied for ten seconds such that the plate electrode has negative potential.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

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 variable attenuator device is disclosed that may be magnetically and latchably controlled such that it does not require a continuous power supply to maintain a particular loss level. The variable attenuator comprises two optical components disposed in spaced apart relation to define a gap between them and a magnetic shutter positioned within the gap. The shutter is movable, due to its magnetic properties, from a first position to at least a second position, where the second position may be within, partially within, or outside of the gap. A mechanism is provided for magnetizing or actuating the shutter to cause it to move from the first position to the at least second position. When the shutter is in the first position, it causes a certain amount of attenuation in the signal being transmitted between the two optical components, and when it moves to the at least second position, a different amount of attenuation is caused, such that movement of the shutter causes a variation in the attenuation.

Abstract: An optical attenuating isolator obtained by combining an optical attenuator and an isolator into a module, is provided. The optical attenuating isolator includes a first collimator, an optical attenuating filter, an isolation unit, and a second collimator. The first collimator is connected to a first optical transmission medium, and collimates light received via the first optical transmission medium. The optical attenuating filter attenuates the output light of the first collimator. The isolation unit receives light attenuated by the optical attenuating filter and passes only polarized light which is polarized in a predetermined specific polarization direction. The second collimator is connected to a second optical transmission medium, and collimates polarized light which has passed through the isolation unit, and transmits the resultant light to the second optical transmission medium.

Abstract: Disclosed is a Faraday rotator capable of reducing the temperature dependence on a Faraday rotation angle, thereby enhancing the temperature characteristic, particularly, in a service environment in which the magnetization direction is variable, and an optical device using the Faraday rotator. The Faraday rotator includes a Faraday element which rotates the polarization plane of polarized light rays passing through the Faraday element when an external magnetic field is applied to the Faraday element.

Abstract: A spatial light modulation device is formed by creating at least one movable element, fixedly attached to the substrate at a first end, from a soft magnetic material with an anisotropic stress created within the movable element such that the element exists in a first position as a result of the anistropic stress and an actuating device comprising a magnetic layer placed within close correspondence with the soft magnetic material for placing the soft magnetic material into a second position.

Abstract: A variable optical attenuator comprises a Faraday rotator including a ferromagnetic garnet film disposed input/output single mode optical signal paths. A collimating/lensing arrangement is used to focus the optical signal between the input/output signal paths and the ferromagnetic garnet film. The ferromagnetic material exhibits multiple types of magnetic domain such that an optical signal will experience ±rotation as its passes through the film. A 90° garnet film thus provides ±90° rotation, resulting in a fill 180° directional difference between the optical signal components. The amplitudes of these signals will thus cancel, providing an essential “full” attenuation of the optical signal. The application and adjustment of a magnetic field to the garnet film controls the strength (i.e.

Abstract: An optical modulator using an isolator, and an optical transmitter including the same are provided. The optical modulator modulates a carrier wave generated by an optical source according to a predetermined electrical signal. An isolator in the modulator includes a Faraday rotator in which the rotation angle of polarization is different according to the intensity of an applied magnetic field. The rotator controls isolation of an optical signal according to the polarization rotation angle and outputs a modulated optical signal. A magnetic field generator produces a magnetic field whose intensity is controlled by a predetermined electrical signal, and applies the produced magnetic field to the isolator. A signal generator supplies the electrical signal to the magnetic field generator and controls the intensity of the electrical signal.

Abstract: A Faraday rotation angle varying apparatus for controlling a Faraday rotation angle of a light beam passing through a garnet single crystal having a Faraday effect by applying external magnetic fields to the garnet single crystal in two or more of directions and varying a synthetic magnetic field synthesized from the external magnetic fields is disclosed. According to an aspect of the present invention, the garnet single crystal has the (111) plane polished and the light beam is allowed to pass through the garnet single crystal along the <111> direction of the garnet single crystal perpendicular to the (111) plane. A displacement path of a synthetic vector of the external magnetic fields is within a fan-shaped range (peripheral lines of the fan-shape inclusive) of a stereographic projection chart of the garnet single crystal with the (111) plane taken as the center of the chart.

Abstract: A reflective Faraday-based optical system is formed to include a partially transmissive optical reflector so that a portion of the optical signal propagating through the system will not be reflected but instead used as an input signal to a monitoring system. The partially transmissive reflector is configured to transmit only a relatively small portion of the optical signal (about 1-10%) so that the performance of the system is not affected. The optical monitoring arrangement may comprise one or more photodetectors, optical fibers, or other optical components for capturing the transmitted signal and converting into an electrical representation that can be evaluated to monitor the power in the optical signal.

Abstract: A low magnetic saturation type bismuth-substituted rare-earth iron garnet crystal film of the invention is grown on a substrate of (111) garnet single crystal (GdCa)3(GaMgZr)5O12 by using a liquid phase epitaxial method. This single crystal has a lattice constant of 1.2497.+-.0.0002 nm and has a chemical structural formula expressed byTb.sub.3-x Bi.sub.x Fe.sub.5-y-z Ga.sub.y Al.sub.z O.sub.12wherein x has the range 1.25<.times.<1.40, y+z has the range 0.50<y+z<0.65, and z/y has the range 0.45<z/y<0.75.

Abstract: A specific polarized light component out of a light wave passed through a magneto-optic crystal (for example YIG) is extracted by a polarizer. The intensity of the light beam output from the polarizer depends on strength and direction of magnetic fields applied to the magneto-optic crystal. The magneto-optic crystal is applied with a first and a second magnetic field acting in directions different from each other and the strength of the composite magnetic field of them is set to exceed a predetermined value at all times. By varying at least one of the first and second magnetic fields, the attenuation factor in the magneto-optic crystal can be changed continuously and with good reproducibility.

Abstract: The present invention provides an optical device making use of a magneto-optical effect. The optical device comprises: a reflector for reflecting an input beam as a reflected beam; a magneto-optical crystal provided so as to pass the input and reflected beams; a first unit for applying a magnetic field to the magneto-optical crystal; and a second unit for varying the magnetic field in accordance with a control signal. The configuration described above allows a small magneto-optical crystal to be used and, thus, a small-size and a low-cost Faraday rotator to be provided. By adding a polarizer to such a Faraday rotator, a variable optical attenuator can be obtained. In particular, by employing a wedge plate as the polarizer, a polarized-independent optical attenuator can be provided.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: An optical isolator comprises two polarizers arranged before and after an optical rotator and a magnet surrounds the optical rotator. The magnet may generate a magnet field with a direction in spatial space parallel to the propagation direction of light traveling in the optical rotator and a strength sufficient to rotate the light to a predetermined rotation angle. Preferably, the polarizers are birefringent wedges of identical shape and optical properties. The magnet in accordance with the present invention may have a pair of magnetic adapters to generate the desired direction and strength of magnetic field. The direction of magnetic field varies in three-dimension space as the magnet is adjusted. The present invention provides an optical isolator of high isolation for high-volume mass production at a low cost. In particular, it may be easily operated at different wavelengths to achieve desired isolation without sacrifice of other optical properties of the optical isolator.

Abstract: Methods for preparing homogeneous magnetic fluid compositions capable of forming ordered one dimensional structures or two dimensional lattices in response to externally applied magnetic fields are disclosed. The compositions are prepared using improved co-precipitation methods in which the steps of the procedure have been tuned to reduce sample heterogeneity. Fe.sub.3 O.sub.4 particles are coated with a surfactant and dispersed in a continuous carrier phase to form these homogeneous magnetic fluid compositions. The ability of these compositions to generate ordered structures can be tested by holding a magnet near a thin film of the compositions and observing the formation of colors in the region near the magnet. Methods for controlling the characteristic spacing of the ordered structures formed by the composition also are disclosed.

Abstract: A magneto-optical switch having three or more ports and two or more lenses, in which at least two ports share a common lens. In one embodiment, the switch has three ports and two lenses, where two of the ports share one of the lenses. In another embodiment, the switch has four ports and two lenses, where two of the ports share one lens and the other two ports share the other lens. A magnet generates a magnetic field in either of two directions to select one of two operating modes for the switch. Walk-off plates separate light energy into two polarized beams and rotators rotate the polarization states of those beams as a function of the magnetic field. Depending on the direction of the rotation, another walk-off plate is used either to recombine the two polarized beams or to further separate them. Further separated beams are reflected from a mirror, while converged beams are transmitted through the light-transmitting center of the mirror.

Abstract: A Faraday rotator is formed of a bismuth-substituted iron garnet single crystal film on which an antireflection film is formed. The antireflection film includes first, second, and third layers. The first layer is a layer of silicon dioxide. The second layer is a layer of tantalum pentoxide. The third layer is a layer of silicon dioxide. The first, second, and third layers are formed in this order from the atmosphere side on the bismuth-substituted iron garnet single crystal film. The antireflection film may be formed on both of opposing surfaces of the single crystal film.

Abstract: A wideband quasi-optical millimeter-wave resonator achieves a wideband frency operation by using a variable dielectric constant photoconducting lens in a Fabry-Perot resonator. Changing the dielectric constant of the lens creates an associated change in the resonant frequency for a given axial mode.

Abstract: A specific polarized light component out of a light wave passed through a magneto-optic crystal, for example, YIG is extracted by a polarizer. The intensity of the light beam output from the polarizer depends on strength and direction of magnetic fields applied to the magneto-optic crystal. The magneto-optic crystal is applied with a first and a second magnetic field acting in directions different from each other. The strength of the composite magnetic field of the first and the second magnetic fields is set to exceed a predetermined value at all times. By varying at least one of the first and second magnetic fields, the attenuation factor in the magneto-optic crystal can be changed continuously and with good reproducibility.

Abstract: An apparatus which attenuates a light signal polarized in a first direction. The apparatus includes a polarization rotation unit and an output unit. The polarization rotation unit rotates the polarization of the light signal to produce a polarization rotated light signal having a polarization component in the first direction and a polarization component in a second direction which is substantially 90 degrees with respect to the first direction. The output unit passes, as an output signal, the polarization component in the second direction of the polarization rotated light signal and blocks the polarization component in the first direction. The polarization rotation unit includes an electromagnet and a permanent magnet which apply magnetic fields in specific directions with respect to the light path. Various yoke constructions are provided for the electromagnet and the permanent magnet.

Abstract: Method for optical energy transfer and energy guidance uses an electric field to control energy propagation using a class of poled structures in solid material. The poled structures, which may form gratings in thin film or bulk configurations, may be combined with waveguide structures. Electric fields are applied to the poled structures to control routing of optical energy. Techniques include frequency-selective switchable- and adjustable-tunable reflection, splitting, directional coupling, frequency-tunable switching and efficient beam combining, as well as polarized beam combining. Adjustable tunability is obtained by a poled structure which produces a spatial gradient in a variable index of refraction along an axis in the presence of a variable electric field. In one embodiment, the present invention is a method of switching a grating which consists of a poled material with an alternating domain structure of specific period.

Abstract: A Faraday rotator capable of maintaining a Faraday rotation angle always constant regardless of temperature variations. The Faraday rotator includes a magneto-optic crystal provided in a light propagation path, a permanent magnet for generating a magnetic field parallel to the light propagation path, and an electromagnet for generating a magnetic field orthogonal to the light propagation path. The strength of a synthetic magnetic field by the permanent magnet and the electromagnet is set to a magnitude large enough to magnetically saturate the magneto-optic crystal. The electromagnet is driven by a drive circuit. The Faraday rotator further includes a temperature sensor provided adjacent to the Faraday rotator, and a controller incorporating data on temperature dependence of a Faraday rotation angle of the magneto-optic crystal to control the drive circuit so that the Faraday rotation angle becomes constant according to a temperature detected by the temperature sensor.

Abstract: An optical isolator device is provided which is free from polarization dispersion. The optical isolator device presents an optical path which is equidistant for both an ordinary ray and an extraordinary ray. The optical isolator device of the present invention comprises a first and second optical isolator, each of identical thickness and each comprising a birefringent for separating an ordinary ray and an extraordinary ray, a polarization rotator for rotating the plane of polarization of these rays and a birefringent for continuing the ordinary ray and the extraordinary ray. In an embodiment of the present invention, an optical isolator device comprises two optical isolators in series, each comprising a first birefringent element for separating an input beam into an ordinary ray and an extraordinary ray, a polarization rotor for rotating the planes of polarization of the ordinary and extraordinary rays by (2m .+-.1/2).times.

Abstract: A Faraday rotator which includes a magnetic optical element and a magnetic field generating unit. The magnetic optical element has an optical path extending therethrough. The magnetic field generating unit is positioned so as not to obstruct the optical path, and generates a uniform magnetic field in the magnetic optical element. The magnetic field generating unit can include a first magnet unit and a second magnet unit. The first magnet unit is positioned so as not to obstruct the optical path and generates a magnetic field passing through the magnetic optical element. The second magnet unit is positioned so as not to obstruct the optical path and generates a magnetic field passing through the magnetic optical element. The magnetic field generated by the second magnet unit is perpendicular to the magnetic field generated by the first magnet unit and combines with the magnetic field generated by the first magnet unit to produce a uniform magnetic field in the magnetic optical crystal.

Abstract: A Faraday rotator for rotating a plane of polarization of polarized light, said Faraday rotator having an optical element comprising a rod which is comprised of an optically transmitting composition comprising cadmium, zinc, and tellurium, and preferably from about 30 wt. % to about 48 wt. % cadmium, from about 2 wt. % to about 20 wt. % zinc, and about 50 wt. % tellurium. This Faraday rotator is especially useful an optical isolator for preventing feedback of transmitted light waves.

Abstract: An optical isolator has a low-profile construction. Two rod-like permanent magnets are on two sides of a Faraday element in parallel to an optical axis. The two permanent magnets are sandwiched and fixed between two ferromagnetic frames each having a light path hole therein. The ferromagnetic frames are each provided with a protrusion for guiding the magnetic flux generated by the permanent magnets to the Faraday element.

Abstract: A Voigt optical filter. Crossed polarizers are provided at the entrance and exit of a vapor cell continuing an alkali metal vapor. A magnet provides a magnetic field at 90.degree. with the axis of the cell and 45.degree. with each polarizer direction. The only light which passes through the filter is light within a narrow frequency band near the atomic transitions (absorption peaks) of the alkali metal vapor.

Abstract: A compact Faraday rotator and isolator featuring a uniform magnetic field for isolating a light source from light which is directed back towards the light source. The isolator comprises a Faraday rotator between two polarizers in a uniform magnetic field. The uniform magnetic field is generated by two pairs of polyhedral shape magnets on opposite sides of the isolator's optical axis. The optical axis passes through a block of Faraday rotator material. One pair of magnets is disposed above the optical axis and the other pair of magnets is disposed below the optical axis. Opposite poles of the magnets are adjacent to each other on the same side of the optical axis and like poles of the magnets face each other across the optical axis, the direction of magnetization of each magnet being generally normal to the optical axis.

Abstract: Method for optical energy transfer and energy guidance uses an electric field to control energy propagation using a class of poled structures in solid material. The poled structures, which may form gratings in thin film or bulk configurations, may be combined with waveguide structures. Electric fields are applied to the poled structures to control routing of optical energy. Techniques include frequency-selective switchable- and adjustable-tunable reflection, splitting, directional coupling, frequency-tunable switching and efficient beam combining, as well as polarized beam combining. Adjustable tunability is obtained by a poled structure which produces a spatial gradient in a variable index of refraction along an axis in the presence of a variable electric field. In one embodiment, the present invention is a method of switching a grating which consists of a poled material with an alternating domain structure of specific period.