Abstract: An optical switch in a one-dimensional multilayer dielectric stack having a photonic band gap, composed of at least two groups of layers of dielectric material whose operating wavelength is near the edge of said photonic band gap. At least one layer of each of the groups is composed of a nonlinear c.sub.3 dielectric material, which creates an intensity-dependent shift in the location of the band gap and produces a dynamical change in the transmissive and reflective properties of the multilayer dielectric stack in response to changes in the intensity of light or the transmittance of electromagnetic radiation passing through the multilayer dielectric stack. The width of the photonic band gap is determined by the differences between the refractive indices of the nonlinear dielectric material and that of the other layers of dielectric material in the multilayer dielectric stack.

Abstract: An optical fiber sensor which is adapted for use in combination with a horseshoe-type iron core comprises a substrate having a groove pattern established by a pair of elongated spaced, parallel grooves, and a third groove which intersects the paired grooves at right angles. An optical fiber having a U-shaped portion is inserted into and fixed in the groove pattern, and an optical modulation unit, which is fixedly provided in a light path of the optical fiber, is placed in the third groove. The substrate is a composite which comprises a non-magnetic portion and soft magnetic portions fixed to either side of the non-magnetic portion. The paired elongated grooves are formed in the soft magnetic portions, while the optical modulation unit is fixed to the non-magnetic portion. A method for making such a composite substrate is also described.

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: Optical isolator, circulator, switch or the like, including a Faraday rotator to which a magnetic field is applied which is oriented along the direction of propagation of light and which is arranged between a preceding polarization filter and a succeeding polarization filter whose planes of polarization enclose an angle with respect to each other such that light can only traverse in one direction, the Faraday rotator having different propagation constants .beta..sub.TE and .beta..sub.TM in a TE plane and a TM plane, respectively. The elaborate technique for adapting the propagation constants of the TE wave and the TM wave is mitigated in that the TE plane of the Faraday rotator is aligned in such a way that it extends between the planes of polarization of the polarization filters.

Abstract: A surface magnetostatic wave device includes an Fe-containing garnet single crystal film grown on a gadolinium gallium garnet substrate. The crystallographic plane azimuth of the gadolinium gallium garnet substrate can be one of a (110) plane, a (100) plane, and a (211) plane. The device achieves both a reduced saturation magnetization and a reduced anisotropic magnetic field to thereby minimize the lowest frequency in the propagation band.

Abstract: An improved fiber optic sensor system and integrated sensor bearing assembly for detecting movement or position of a rotating wheel bearing having a multi-pole tone ring which produces an alternating magnetic field indicative of movement and position of the rotating member. A magneto-optical material, such as a bismuth garnet iron (B.I.G.) crystal, having discrete magnetic domains is positioned in the vicinity of the tone ring so that the domains align themselves to the magnetic field generated by the tone ring. A single fiber optic cable, preferably single mode fiber, carries light generated by a source of light to the B.I.G. crystal. The light passes through the B.I.G. crystal and is refracted at domain boundaries in the crystal. The intensity of the refracted light is indicative of the amount of alignment of the domains and therefore the strength of the magnetic field.

Abstract: Integrated optical devices which utilize a magnetostrictively, electrostrictively or photostrictively induced stress to alter the optical properties of one or more waveguides in the device are disclosed. The integrated optical devices consist of at least one pair of optical waveguides preferably fabricated in a cladding material formed on a substrate. A stress applying material, which may be a magnetostrictive, electrostrictive or photostrictive material, is affixed to the upper surface of the cladding material near at least one of the optical waveguides. When the appropriate magnetic, electric or photonic field is applied to the stress applying material, a dimensional change tends to be induced in the stress applying material. The constrained state of the stress applying material, however, caused by its adhesion to the cladding material, causes regions of tensile and compressive stress, as well as any associated strains, to be created in the integrated optical device.

Abstract: In accordance with the invention, an optical fiber phase shifter comprises a length of asymmetrical optical fiber disposed perpendicular to a magnetic field for providing a non-reciprocal phase shift. Preferably the fiber is wound in a circular coil and exposed to an axial field as from a pancake magnet. In an isolator, the fiber length and magnet strength are chosen to provide non-reciprocal phase shifts of .+-.45.degree. or .+-.90.degree.. The isolator including the phase shifter can be any of several configurations.

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: A method of magneto-optically modulating light comprises the steps of linearly polarizing the light on its transmission path, placing a magnetooptic effect element on the transmission path of the polarized light with the spontaneous magnetization direction of the element being parallel with the transmission path, the polarized light being modulated into a first light component when the plane of polarization of the polarized light is rotated to assume the first rotational position by the magnetooptic effect element in the absence of the applied magnetic field, applying the magnetic field to the magnetooptic effect element with the internal magnetization of the element being oriented in a direction perpendicular to the transmission path, the polarized light being modulated into a second light component when the plane of polarization of the polarized light is shifted to a second rotational position by the magnetooptic effect element in the presence of the applied magnetic field.

Abstract: An optical non-reciprocal circuit is constituted by a channel waveguide, a planar waveguide, and a diffraction lattice or grating. The channel waveguide is disposed in a planar substrate that is transmissive to optical waves. The planar waveguide is disposed on only one side of a substrate plane divided by the channel waveguide in the substrate plane and having an equivalent refractive index lower than that in the channel waveguide. The diffraction grating provides a spatial periodic change of the refractive index to a guided optical wave of the channel waveguide. The periodicity of the lattice direction, that is, the direction of the wavenumber vector is neither parallel nor perpendicular to the optical transmission direction of the channel waveguide but is given a finite angle. The optical non-reciprocal circuit can be realized by using only an ordinary dielectric material with the circuit being highly productive and low priced and having high performance.

Abstract: An optical article exhibits effects attributable to the nonlinear second order polarizability of electromagnetic radiation and comprises a polymer containing within its repeating units polar aligned noncentrosymmetric molecular dipoles having an electron donor moiety linked through a conjugated .pi. bonding system to an electron acceptor moiety to permit oscillation of the molecular dipoles between a ground state exhibiting a first dipole moment and an excited state exhibiting a different dipole moment, characterized in that the molecular dipoles include as an acceptor moiety a vinyl group geminally substituted by two strong electron withdrawing groups, at least one of which is a sulfonyl moiety.

Abstract: In a polarization rotator device, a thin-film magneto-optic medium is magnetized by a thin-film magnet. To serve as an optical isolator, the device may include polarizers. In such an optical isolator, in which the magneto-optic medium was formed as a Bi-YIG triple-layer structure, and the thin-film magnet as a single-crystal iron-cobalt layer, an extinction ratio better than -20 dB was realized.

Abstract: An optical device which optically connects a first and a second optical fiber with an optical path provided therebetween and has two or more functions including the function of an optical isolator. A beam of parallel rays obtained by having a beam from an excitation end of a first optical fiber collimated by a lens is passed through a double refraction element, a magnetooptic element, and a double refraction element in order of mention and converged by a lens to be introduced to a second optical fiber through its excitation end, while a beam from the second optical fiber is not coupled to the first optical fiber. Meanwhile, a beam from an excitation port is coupled to the first optical fiber. The optical device is suitable for use in an optical amplification system and a two-way optical transmission system.

Abstract: There is provided an optical circulator (16) for bidirectional communication on a fiber optic communication transmission system. Polarization preserving single-mode fiber lengths (26), (28) connect all-fiber polarization splitter (18) with the Faraday single-mode fiber lengths (22), (24). Polarization preserving single-mode fiber lengths (30), (32) connect the opposite ends of Faraday single-mode fiber lengths (22), (24) with all-fiber polarization splitter (20). A communication transmitter is connected to splitter (18) at port 1, and a communication receiver is connected to splitter (18) at port 3. A fiber optic communication link (50) is connected to splitter (20) at port 2. The components of optical circulator (16) cooperate such that light transmitted into port 1 exits from port 2, and light transmitted into port 2 exits from port 3.

Abstract: A ferrofluid controlled switch for a light pipe has a light pipe having a first index of refraction, a fluid responsive to a magnetic field having a second index of refraction, and an enclosure concentrically located around at least a portion of the light pipe for retaining the fluid such that the fluid is capable of assuming two configurations, one adjacent to the light pipe and one separate from the light pipe. A controllable magnetic field device such as a permanent magnet or wire coils are used to transfer the magnetically responsive fluid between said two configurations to reduce the output of the light pipe when the fluid is adjacent to the light pipe.

Abstract: Magneto-optical waveguide having a magneto-optical layer (5) applied on a substrate layer (4). An accurate phase match is provided at a compact structure in that a thin layer is applied in uniform thickness on the overall surface area of the magneto-optical layer (5), which thin layer consists of an optically transparent non-metallic material and whose refractive index is less than the refractive indices of the magneto-optical layer (5) and of the substrate layer (4), and whose thickness is less than 0.3 .mu.m.

Abstract: There is provided a magnetooptic device including a substrate; a semiconductor layer having a quantum well structure formed on the substrate, in which the semiconductor layer is formed by alternately laminating a well layer and a barrier layer and at least the barrier layer in those layers contains magnetic ions; and electrodes to apply an electric field to the semiconductor layer. A light which was polarized in a predetermined direction is input to the semiconductor layer. A magnetic field is applied to the semiconductor layer. An electric field is applied to the semiconductor layer by the electrodes. The light which was transmitted in the semiconductor layer is extracted. A degree of leakage of a wave function of the carrier in the well layer into the barrier layer changes. An effective magnetic field which a carrier spin feels changes by an exchange interaction between the carrier spin and a magnetic moment associated with the magnetic ions.

Abstract: An optical isolator having three or four birefringent crystals and two magneto-optic elements is disposed between two light waveguides to prevent reverse-directed light from returning to the light waveguide on the light-source side. Forward-directed light emitted from the light waveguide on the light-source side is allowed to properly enter into the other light waveguide, whereas the reverse-directed light returning reflectively toward the light waveguide on the light-source side is separated into two polarized component and undergoes polarization rotation while propagating in the optical isolator, to thereby advance out of the optical axis of the light-source side light waveguide.