Abstract: An optical waveguide device includes a substrate having an electro-optical effect, an optical waveguide formed on the substrate, an electrode provided for the optical waveguide, a monitoring optical waveguide for guiding part of light outputted from the optical waveguide as monitor light, an attenuation section provided for the monitoring optical waveguide for attenuating the monitor light, and a light detection section for detecting the intensity of the monitor light guided by the monitoring optical waveguide and attenuated by the attenuation section.

Abstract: An optical modulator of the Mach-Zehnder type including electrodes disposed above a substrate having a pair of linear portions of an optical waveguide includes a signal electrode to which modulating signals are applied; first and second earth electrodes; and a bias electrode to which a bias signal for controlling an operating point of the modulating signals is applied. The earth electrodes are disposed at either side of the signal electrode disposed above one of the linear portion, and the first earth electrode is disposed above the other linear portion. The bias electrode is disposed adjacent to the first earth electrode on a side opposite to the signal electrode. The bias electrode is disposed on a surface of the substrate, and a buffer layer is formed on the bias electrode. The first earth electrode has a ladder shape having the bias electrode interposed between the two long portions of the ladder.

Abstract: An optical modulator includes a signal electrode for application of modulation signals whereby light propagated over an optical waveguide is modulated, and bias electrodes for application of a bias voltage for controlling an operating point for the modulation signals. A buffer layer is provided between a substrate exhibiting electro-optical effect and the bias electrodes, but at regions where no optical waveguide is formed beneath the bias electrodes, no buffer layer is provided, and the bias electrodes are provided directly upon the substrate. This configuration enables bias voltage to be reduced.

Abstract: An optical waveguide is formed by diffusing a second impurity to form a second diffusion area having a large refractive index on a substrate. A groove is formed at a portion of the substrate corresponding to an outside of a bend of a bent portion along the second diffusion area. A first diffusion area is formed by diffusing a first impurity from a bottom of the groove to reduce a refractive index of the substrate.

Abstract: An optical waveguide has a diffusion area (optical waveguide) with a high refractive index formed by diffusing impurities on a substrate. The diffusion area has a bent portion, and the optical waveguide includes: a groove formed by cutting the substrate along the diffusion area on the outside of the bent portion of the diffusion area; and a first buffer layer disposed on the upper portion of the diffusion area, having a refractive index equal to or higher than the refractive index of the substrate. The optical waveguide includes a second buffer layer having a refractive index equal to or lower than the refractive index of the substrate on the upper portion of the first buffer layer, and the second buffer layer is formed including contact with a side face of the groove.

Abstract: In an optical modulator according to the present invention, a Mach-Zehnder optical waveguide is formed on a substrate having an electro-optic effect, a signal electrode and an earth electrode are disposed along a pair of branching waveguides of the optical waveguide, and an electric signal is applied on the signal electrode to thereby modulate a light being propagated through the optical waveguide. At this time, a first region and a second region are set in an interacting portion where the light and the electric signal interacts to each other, to form a polarization inversion region in each of the set regions, and also, an arrangement pattern of the signal electrode is determined so that a modulation direction in each of the set regions is opposite to each other. As a result, it is possible to realize the optical modulator of simple configuration capable of realizing simultaneously the broad modulation band and the wavelength chirping suppression.

Abstract: An optical communication device includes a substrate which has electro-optical effect; a first optical modulator which has a pair of waveguides formed in the substrate; a second optical modulator which has a pair of waveguides formed in the substrate; a waveguide coupler which is provided in an output of the first optical modulator, the waveguide coupler being able to couple and branch light propagating through the pair of waveguides of the first optical modulator; and a delay connecting section which gives differential delay to the output branched by the waveguide coupler and inputs the output to the pair of waveguide of the second optical modulator. As a result, the optical communication device and optical device in which insertion loss is reduced compared with the conventional optical modulator can be provided.

Abstract: In an optical modulator according to the present invention, a Mach-Zehnder optical waveguide is formed on a substrate having an electro-optic effect, a signal electrode and an earth electrode are disposed along a pair of branching waveguides of the optical waveguide, and an electric signal is applied on the signal electrode to thereby modulate a light being propagated through the optical waveguide. At this time, a first region and a second region are set in an interacting portion where the light and the electric signal interacts to each other, to form a polarization inversion region in each of the set regions, and also, an arrangement pattern of the signal electrode is determined so that a modulation direction in each of the set regions is opposite to each other. As a result, it is possible to realize the optical modulator of simple configuration capable of realizing simultaneously the broad modulation band and the wavelength chirping suppression.

Abstract: An intake port for a 4-cycle engine includes an intake port base integrally formed with a cylinder head, and an intake port forming member that forms an intake port together with the intake port base. The area of the cross section of the intake port orthogonal to a centerline of the intake port is substantially uniform from an open intake side thereof toward a combustion chamber. The angle made by the centerline of the intake port and an intake valve shaft is larger than 90° from a viewpoint of the intake valve. Thereby, the 4-cycle engine can output high power with the intake port shape, as formed with above mentioned configuration, that reduces intake resistance and that uses simple design molds. More specifically, the engine can reliably prevent condensed fuel from remaining in the intake port to avoid incomplete combustion of gas.

Abstract: A portable 4-cycle engine with a configuration which allows cooling air to flow in the direction of the crankshaft relative to a cylinder head on a cylinder, and a portable machine equipped with this engine, are provided, respectively. In such an engine, the cylinder is separated from the cylinder head including a combustion chamber formed at the cylinder side therein. The engine further comprises a valve train area formed in the cylinder head at the downwind side of the cooling air, and a plurality of vertical fins protruding upward from the cylinder head and extending in the direction of the crankshaft. The valve train area and the plurality of vertical fins are all integrally formed with the cylinder head, so that the cylinder head can be made thinner and lighter with high rigidity to enable the portable machine to become smaller, lighter, and more powerful.

Abstract: The present invention provides an optical waveguide device wherein a driving voltage to be applied is reduced. The optical waveguide device comprises a substrate cut in a Z-axis direction and having an electro-optical effect, an interference type optical waveguide formed on the substrate for causing lights which propagate along a plurality of parallel optical waveguides to interfere with each other, and a lumped-constant type electrode for applying a voltage for the electro-optical effect to the light propagating along the optical waveguides which form the interference type optical waveguide. The lumped-constant type electrode complements potentials to be supplied to adjacent ones of the plurality of parallel optical waveguides to each other such that voltages having an equal absolute value but having the opposite signs are applied to the adjacent optical waveguides. The apparatus of the present invention is applied to, for example, an optical communication system.

Abstract: An optical waveguide is formed on a substrate and includes a curved ridge structure, a curved optical path, and a buffer layer. The curved ridge structure is formed on the substrate so as to have a curvature in a longitudinal direction of the curved ridge structure. The curved optical path is formed along the curved ridge structure. The buffer layer covers a side of the ridge structure and has a lower refractive index than a refractive index of the substrate.

Abstract: In relation to an optical modulator (e.g., an RZ optical modulator) formed from a plurality of Mach-Zehnder optical modulators, in an attempt to make the optical modulator compact and realize a low drive voltage, the optical modulator is formed by comprising a plurality of Mach-Zehnder optical modulators, each including a substrate exhibiting an electro-optical effect, an optical waveguide formed on the substrate, and electrodes formed in the vicinity of the optical waveguide. The plurality of Mach-Zehnder optical modulators are arranged on the substrate and connected into multistage.

Abstract: An optical device having a substrate having an electro-optical effect, an optical waveguide formed in the substrate, and an electric field emission electrode, and an electric field convergence electrode to which an electric field emitted from the electric field emission electrode converges. The optical waveguide is formed such that light propagating through the optical waveguide passes through an area under the electric field emission electrode or an area under the electric field convergence electrode and then passes through a remaining electrode. As a result, even when an interaction length is increased, the optical device acquires (increases) a modulation index appropriate to the increase in interaction length, thereby diminishing a drive voltage.

Abstract: The present invention relates to an optical modulator capable of preventing a disconnection of an electrode and improving a discontinuity of a characteristic impedance while realizing a polarization inverting area and a ridge waveguide in a single optical modulator. In the optical modulator, a first electrode is composed of an inverting area electrode portion formed on an upper portion of one of first and second waveguides in the polarization inverting area, a non-inverting area electrode portion formed on an upper portion of the other one of the first and second waveguides in the other area, and a connection portion for making a connection between the inverting area electrode portion and the non-inverting area electrode portion at the boundary between the polarization inverting area and the other area. A supporting mechanism for supporting the connection portion of the first electrode is provided in a groove.

Abstract: An object of the present invention is to provide an optical device, in which a stress applying on ridge sections caused by the difference of thermal expansion between a metal film of which a ground electrode is formed and a substrate is reduced. In order to achieve this, in the optical device of the present invention, the ratio of the volume of a ground electrode portion formed at the position of other groove to the area of opening part of the other groove is smaller than the ratio of the volume to the area of a ground electrode portion formed at the position except the other groove.

Abstract: An object of the invention is to provide a Mach-Zehnder type optical modulator that can reduce wavelength chirp occurring in a modulated light, and also can reduce an optical loss with a small sized configuration. To this end, according to the present Mach-Zehnder type optical modulator, in a configuration where optical waveguides and a coplanar electrode are formed on a substrate having an electro-optical effect, a polarization inversed region is formed in a part of an interaction portion of the substrate, and a signal electrode is arranged above one of parallel waveguides in a polarization inversed region and is arranged above the other parallel waveguide in a non-inversed region. Furthermore, a surface area of the substrate positioned on both sides of each of the parallel waveguides is lowered to provide a ridge structure section, and a buffer layer is formed on a ridge side face thereof.

Abstract: An optical communication device includes a substrate which has electro-optical effect; a first optical modulator which has a pair of waveguides formed in the substrate; a second optical modulator which has a pair of waveguides formed in the substrate; a waveguide coupler which is provided in an out put of the first optical modulator, the waveguide coupler being able to couple and branch light propagating through the pair of waveguides of the first optical modulator; and a delay connecting section which gives differential delay to the output branched by the waveguide coupler and inputs the output to the pair of waveguide of the second optical modulator. As a result, the optical communication device and optical device in which insertion loss is reduced compared with the conventional optical modulator can be provided.

Abstract: An optical waveguide is formed on a substrate and includes a curved ridge structure, a curved optical path, and a buffer layer. The curved ridge structure is formed on the substrate so as to have a curvature in a longitudinal direction of the curved ridge structure. The curved optical path is formed along the curved ridge structure. The buffer layer covers a side of the ridge structure and has a lower refractive index than a refractive index of the substrate.

Abstract: The present invention has an object to provide a Mach-Zehnder optical modulator for achieving the reduction of wavelength chirping caused in a modulated light. To this end, according to the present invention, in a Mach-Zehnder optical modulator configured by forming an optical waveguide and a coplanar electrode on a substrate having an electro-optic effect, a polarization inversion region is formed on a part of a portion where lights being propagated through a pair of parallel waveguides and a high frequency electric signal being propagated through a signal electrode interact to each other, and also the signal electrode is arranged on one of the parallel waveguides in the polarization inversion region and is arranged on the other parallel waveguide in a non-inversion region.