Abstract: A method according to an aspect of the present invention, is a method for manufacturing an optical waveguide element, including: an optical waveguide forming step of forming an optical waveguide extending in a first direction in a substrate by doping the substrate with an impurity for reducing a coercive electric field of the substrate, a ridge forming step of forming a first ridge part including the optical waveguide and a second ridge part intersecting the first ridge part, and a poling step of reversing a polarization direction of a region of the substrate divided by the second ridge part by applying voltage to the region.

Abstract: An aspect of the present invention is an optical modulator including an electro-optic substrate, an optical waveguide, and a signal electrode for applying an electric field corresponding to a modulation signal to the optical waveguide. The electro-optic substrate includes a trench portion, which is formed by digging a surface of the electro-optic substrate, and a ridge portion, which is formed in a ridge shape by the trench portion so that an optical waveguide is provided. The trench portion includes a first trench portion, which is a trench portion between a pair of branched optical waveguides, and a second trench portion, which is a trench portion other than the first trench portion. Digging depths of the first and second trench portions are different.

Abstract: An object of the invention is to provide an optical waveguide device which is able to efficiently absorb or remove leaked light propagating in a substrate. An optical waveguide device in which an optical waveguide is formed on a substrate, in which the optical waveguide includes a main waveguide through which signal light propagates, and a metal layer (a bonding layer or an electrode) is formed, through a high refractive index layer having a refractive index higher than the refractive index of the substrate, in at least a part of a region on which the main waveguide is not formed.

Abstract: An object is to provide a light modulator capable of highly accurate bias control by maintaining main output characteristics and monitor characteristics in an appropriate relationship and matching a bias point determined using monitor output and an optimal bias point of main output. The light modulator includes an optical waveguide formed in a substrate having a thickness of 20 ?m or less, in which the optical waveguide includes a Mach-Zehnder waveguide and an output waveguide for guiding signal light from a multiplexing portion of the Mach-Zehnder waveguide and outputting the signal light outside the substrate and monitoring means that monitors signal light or radiated light. Leaked light-removing means for removing some of the radiated light propagating through the output waveguide from the output waveguide and emitting the radiated light outside the substrate is provided in the light modulator.

Abstract: An optical waveguide device in which optical characteristics are less degraded even when a branch angle in a Y branch portion of an optical waveguide is great is provided.

Abstract: An optical control element capable of efficiently removing unnecessary higher mode light without complicating a manufacturing process of the optical control element is provided. The optical control element includes a substrate having an electro-optical effect, optical waveguides that are formed on the substrate, and a control electrode that controls light waves propagating through the optical waveguides, and the optical waveguides include an output waveguide portion which derives fundamental mode light, and a subsidiary waveguide portion which is connected to the output waveguide portion and derives higher mode light, and removal means is formed in contact with the subsidiary waveguide portion, for removing the higher mode light propagating through the subsidiary waveguide portion.

Abstract: An optical waveguide device having a Mach-Zehnder type waveguide formed on a substrate is provided in which a slope of two waveguides input to an optical coupler on an output side of the Mach-Zehnder type waveguide is 0 degrees, a waveguide of the optical coupler after being coupled by the optical coupler is a multi-mode waveguide, and the waveguide which is output from the optical coupler is a three-branched waveguide including an output main waveguide and two output sub waveguides interposing the output main waveguide therebetween.

Abstract: It is an object to provide an optical control device capable of realizing speed matching between a microwave and a light wave or impedance matching of microwaves and of reducing a driving voltage. An optical control device including a thin plate 1 (11) which has an electro-optical effect and has a thickness of 10 ?m or less, an optical waveguide 2 formed in the thin plate, and control electrodes for controlling light passing through the optical waveguide is characterized in that the control electrodes are configured to include a first electrode and a second electrode disposed to interpose the thin plate therebetween, the first electrode has a coplanar type electrode including at least a signal electrode 4 and a ground electrode 5, and the second electrode has at least a ground electrode 54 (55, 56) and is configured to apply an electric field to the optical waveguide in cooperation with the signal electrode of the first electrode.

Abstract: An optical control element capable of efficiently removing unnecessary higher mode light without complicating a manufacturing process of the optical control element is provided. The optical control element includes a substrate having an electro-optical effect, optical waveguides that are formed on the substrate, and a control electrode that controls light waves propagating through the optical waveguides, and the optical waveguides include an output waveguide portion which derives fundamental mode light, and a subsidiary waveguide portion which is connected to the output waveguide portion and derives higher mode light, and removal means is formed in contact with the subsidiary waveguide portion, for removing the higher mode light propagating through the subsidiary waveguide portion.

Abstract: It is intended to suppress the influence of a photorefractive phenomenon or the coupling of stray light to signal light. A Mach-Zehnder waveguide type optical modulator is provided which includes a thin plate 1 with a thickness of 20 ?m or less formed of a material having an electro-optical effect, an optical waveguide 2 formed on a front surface or a rear surface of the thin plate, and a modulation electrode modulating light passing through the optical waveguide. The optical waveguide includes an input optical waveguide 21, branched optical waveguides 23 to 28, and an output optical waveguide 30. The branched optical waveguide includes an input branching portion (region B) in which the input optical waveguide is branched into a plurality of optical waveguides, an output merging portion (region D) in which the plurality of optical waveguides connected to the output optical waveguide are merged, and a parallel portion (region C) formed between the input branching portion and the output merging portion.

Abstract: An optical waveguide device having a Mach-Zehnder type waveguide formed on a substrate is provided in which a slope of two waveguides input to an optical coupler on an output side of the Mach-Zehnder type waveguide is 0 degrees, a waveguide of the optical coupler after being coupled by the optical coupler is a multi-mode waveguide, and the waveguide which is output from the optical coupler is a three-branched waveguide including an output main waveguide and two output sub waveguides interposing the output main waveguide therebetween.

Abstract: Disclosed is an optical element which includes a support substrate and a thin plate of single crystal stacked on the support substrate through a thermoplastic adhesive, having the advantages of easily regulating the phase of light waves and restoring the regulated state to the original state. The optical element includes a support substrate 4 and a thin plate 1 of single crystal stacked on the support substrate 4 through a thermoplastic adhesive 3. The optical characteristics of the optical element are regulated by applying stress within an elastic limit to at least a part of the thin plate in a state where the thermoplastic adhesive is softened by heating the optical element, forming a concavo-convex part 10 in the thin plate, and then cooling the optical element to fix the concavo-convex part.

Abstract: The waveguide-type polarizer includes: a Z-cut lithium niobate substrate; an optical waveguide having a ridge structure and formed on the substrate; a low refractive index film formed with a thickness satisfying 0?n·t/??0.3742 (where n is a refractive index, t (?m) is the thickness of the film, and ? (?m) is the wavelength of a light wave) on the side of the ridge structure; and a high refractive index film formed with a thickness satisfying 0.089?n·/? on the low refractive index film. The width of the ridge structure is a ridge width where the distribution of ordinary light of the light waves propagated through the optical waveguide changes and the distribution of extraordinary light of the light waves does not change, the angle of the ridge structure is less than 90°, and the waveguide-type polarizer has a function of transmitting extraordinary light.

Abstract: To provide an optical device sealing structure capable of simply sealing an optical fiber inserting portion. Provided is a structure that seals an optical device including a metallic case having an optical element disposed therein and an optical fiber inserted through a through hole of the case, wherein a Zn-containing surface is formed on a surface of a bare fiber portion that is formed by partly removing a coating of the optical fiber so as to expose a bare fiber, and wherein an Sn-containing sealing material is charged between the Zn-containing surface and an inner wall of the through hole.

Abstract: To provide an optical waveguide device which can allow a light-receiving element to be precisely aligned with a diffused waveguide formed in a dielectric substrate to implement an evanescent coupling light-receiving element. An optical waveguide device includes a dielectric substrate 1, a diffused waveguide 2 formed by thermally diffusing a high-refractive material into the dielectric substrate, and a light-receiving element 4 which is disposed above the diffused waveguide and which receives a part of an optical wave propagating in the diffused waveguide. Here, at least a part 3 of a pedestal 3 and 5 supporting the light-receiving element above the dielectric substrate is formed by disposing the high-refractive material in a predetermined pattern in the vicinity of the diffused waveguide and thermally diffusing the high-refractive material at the same time as forming the diffused waveguide.

Abstract: Disclosed is an optical waveguide element wherein a plurality of Mach-Zehnder waveguides to be used for DQPSK modulation and the like are integrated on a thin substrate and the on/off extinction ratio is improved. The optical waveguide element has the thin board, which is formed of a material having electrooptical effects and has a thickness of 20 ?m or less, and an optical waveguide formed on the front surface or the rear surface of the thin board. The optical waveguide has the plurality of Mach-Zehnder waveguide sections, and multiplexes optical waves outputted from two or more Mach-Zehnder waveguide sections. In the multiplexing section in each Mach-Zehnder waveguide section (MZA), a triply branched waveguide, which is composed of a waveguide for output (c1) and two waveguides for radiation (b1, b2) disposed to sandwich the waveguide for output, is formed.

Abstract: A method of adjusting the optical axis of an optical waveguide element which can improve a manufacturing yield of the optical waveguide element, an alignment yield between the optical waveguide element and an input waveguide means, etc. and can equalize the branch ratio in a Y-branch waveguide; and an optical waveguide element which can be made compact and also inhibited from complication in structure by using this method. The optical waveguide element (5) formed on a substrate comprises at least a linear waveguide (6) and a Y-branch waveguide (7) branched from the linear waveguide.

Abstract: In order to provide an optical modulator capable of suppressing generation of mode mismatching light in the Y-multiplexer in the MZ-type waveguide or mixing of the mode mismatching light with the radiation-mode light or the output light, and separately extracting output light and radiation-mode light, there is provided an optical modulator having a Mach-Zehnder type waveguide on a surface of a dielectric substrate, wherein a waveguide after multiplexing in a Y-multiplexer in an output side of the Mach-Zehnder type waveguide is a multiple mode waveguide 2, a subsidiary output waveguide as a high-order mode waveguide 2 is connected to a portion where the multiple mode waveguide is changed to a main output waveguide 3 as a single mode waveguide, and the multiple mode waveguide 2 has a length equal to or longer than 150 ?m.

Abstract: The waveguide-type polarizer includes: a Z-cut lithium niobate substrate; an optical waveguide having a ridge structure and formed on the substrate; a low refractive index film formed with a thickness satisfying 0?n·t/??0.3742 (where n is a refractive index, t (?m) is the thickness of the film, and ? (?m) is the wavelength of a light wave) on the side of the ridge structure; and a high refractive index film formed with a thickness satisfying 0.089?n·/? on the low refractive index film. The width of the ridge structure is a ridge width where the distribution of ordinary light of the light waves propagated through the optical waveguide changes and the distribution of extraordinary light of the light waves does not change, the angle of the ridge structure is less than 90°, and the waveguide-type polarizer has a function of transmitting extraordinary light.

Abstract: An optical device and a method of manufacturing the optical device, with the method including the steps of forming a dopant layer on a stoichiometric lithium niobate single crystal substrate with Li to Nb mole composition ratio of 49.5% to 50.5%, and diffusing a dopant in the dopant layer into at least a portion of the stoichiometric lithium niobate single crystal substrate. The stoichiometric lithium niobate single crystal substrate includes 0.5 to 5 mol % of Mg. In the diffusing step, a heat treatment is performed at a diffusion temperature of 1000° C. to 1200° C. for a diffusion time of 3 hours to 24 hours in a dry atmosphere of at least one of O2, N2, Ar and He gas having a dew-point temperature of ?35° C. or less.