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 M 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: An optical waveguide device includes: a substrate having an electro-optical effect; an optical waveguide formed on the substrate; and a control electrode for applying an electric field to the optical waveguide. The optical waveguide device has the following characteristics. A thickness of the substrate is 30 ?m or less. The control electrode has a signal electrode and a ground electrode. A low-permittivity layer is formed at least on a surface portion of the signal electrode in contact with the substrate.

Abstract: An object of the invention is to provide a traveling-wave-type optical modulator capable of adjusting the frequency characteristics of an electric/optical conversion response over a wide frequency band, preventing the occurrence of jitter, and improving optical transmission characteristics. A traveling-wave-type optical modulator 20 includes: a substrate that has an electro-optical effect; an optical waveguide that is formed on the substrate; a modulating electrode that controls the modulation of a light wave traveling through the optical waveguide and includes a signal electrode portion 21 and a ground electrode portion; an input interface 22 that is connected to an input side of the signal electrode portion; a terminator 23 that is connected to the end of the signal electrode portion; and an adjustment filter 31 that is provided between the input interface and the signal electrode portion and adjusts frequency characteristics. It is preferable that the adjustment filter 31 be a passive filter.

Abstract: The present invention is directed to provide a light modulation device capable of not only restricting the faint light propagating in the adhesive layer from being re-incident on the thin substrate but also increasing an adhesive strength of the thin substrate and the supplementing plate. The invention is characterized in a light modulation device having a thin substrate 1 made of material with an electro-optical effect and with a thickness of below 20 ?m; an optical waveguide 2 formed on a surface of the thin substrate or the other surface thereof; and a modulation electrode 3 formed on the surface of the thin substrate and for modulating light passing through the optical waveguide, comprising: a supplementing plate 5 adapted to be bonded to the thin substrate via an adhesive layer 4, wherein a bonding surface of the supplementing plate is formed as a rough surface 10 relative to a bonding surface of the thin substrate.

Abstract: An optical modulator is provided which suppresses a radiation mode of a microwave generated in a connection substrate or a termination substrate from entering a signal electrode of the optical modulator and suppresses modulation properties from being degraded. The optical modulator includes an optical modulation element (1) having a substrate with an electro-optic effect, an optical waveguide formed on the substrate, and a modulating electrode (or a signal electrode (2)) for modulating light passing through the optical waveguide; and a connection substrate (4), arranged outside the substrate, for supplying the optical modulation element with a microwave signal operating the optical modulation element. A signal input terminal (22) and a signal output terminal (23) are formed on the connection substrate (20).

Abstract: It is an object of the invention to provide an optical modulator in which a connection substrate or a terminal substrate is disposed outside an optical modulation element and which can maintain at a proper voltage amplitude value a modulation signal applied to an optical modulation element. An optical modulator includes: a substrate having electro-optic effect; an optical waveguide formed on the substrate; an optical modulation element 1 having a modulation electrode (which includes a signal electrode 2) for modulating light passing through the optical waveguide; and a connection substrate 20 disposed outside the substrate to supply a modulation signal for driving the optical modulation element to the optical modulation element.

Abstract: An optical modulator in which stabilized driving is realized over a long time by relaxing stress generated in a recess formed in the surface of a substrate in the optical modulator and controlling deterioration of optical modulation control caused by stress-strain in the substrate including an optical waveguide. The optical modulator comprises a substrate of a material exhibiting electrooptic effect, an optical waveguide (4) provided on the substrate, and control electrodes (20-25) for controlling the phase of light being guided through the optical waveguide characterized in that a recess (12) is provided in the surface of the substrate for forming the control electrodes, and the control electrode (24) being formed on the recess is provided with a stress relaxing means.

Abstract: An optical modulator in which stabilized driving is realized over a long time by relaxing stress generated in a recess formed in the surface of a substrate in the optical modulator and controlling deterioration of optical modulation control caused by stress-strain in the substrate including an optical waveguide. The optical modulator comprises a substrate of a material exhibiting electrooptic effect, an optical waveguide (4) provided on the substrate, and control electrodes (20-25) for controlling the phase of light being guided through the optical waveguide characterized in that a recess (12) is provided in the surface of the substrate for forming the control electrodes, and the control electrode (24) being formed on the recess is provided with a stress relaxing means.