Abstract: Provided is an optical control element that can minimize an optical path difference between branched waveguides while reducing a difference in structure between the branched waveguides by disposing an input portion and an output portion of an optical waveguide on the same side of a substrate on which the optical waveguide is formed.

Abstract: An optical modulator includes a relay substrate having signal conductor patterns that connect input signal terminals and signal electrodes of an optical modulation element and ground conductor patterns, and a housing that accommodates the optical modulation element and the relay substrate. Regarding at least one signal conductor pattern, the two ground conductor patterns sandwiching the signal conductor pattern are formed in an asymmetrical shape in a plan view in a rectangular connection area including a signal connection portion at which the signal conductor pattern and the input signal terminal are connected. The connection area is centered on the at least one signal conductor pattern in a width direction, and has a width equal to a distance to the nearest adjacent signal conductor pattern and a height equal to a distance from an end of the signal connection portion farthest from a signal input side to the signal input side.

Abstract: In order to provide an optical waveguide element that is capable of reducing coupling loss at a coupling portion with an optical fiber and of reducing propagation loss in an optical waveguide, the optical waveguide element comprises a supporting substrate and a waveguide layer consisting of a material having an electro-optic effect stacked on the supporting substrate, wherein a rib portion for forming an optical waveguide is provided protruding on an upper surface of the waveguide layer; a groove portion is formed on an upper surface of the supporting substrate directly below a part of the rib portion; and the groove portion is filled with a material having an effective refractive index comparable to that of the waveguide layer.

Abstract: An optical modulator includes an optical modulation element having a plurality of signal electrodes, a plurality of signal input terminals, a relay substrate on which a plurality of signal conductor patterns that electrically connect the signal input terminals and the signal electrodes and a plurality of ground conductor patterns are formed, and a housing. A signal input side and signal output side of the relay substrate face each other in a plan view, and electromagnetic wave propagation suppressing units that are made of a material that absorbs electromagnetic waves and have a height protruding from a surface of the relay substrate are provided, along at least one side of an end portion of the signal input side and an end portion of the signal output side in the plan view.

Abstract: An optical modulator includes: an optical modulation element that is configured to generate two modulated light beams, each of which is modulated by two sets of electrical signals, and that includes a plurality of signal electrodes; a plurality of signal input terminals, each of which inputs an electrical signal; a relay substrate on which a plurality of signal conductor patterns and a plurality of ground conductor patterns are formed, the relay substrate being configured to propagate the two sets of electrical signals by two pairs of the adjacent signal conductor patterns; and a housing, in which the at least two signal conductor patterns including at least one parts mounting part including electrical circuit elements are configured such that first signal propagation directions, which are signal propagation directions at the parts mounting parts, are different from each other.

Abstract: To provide an optical modulator in which a plurality of Mach-Zehnder type optical waveguides are integrated, which can be driven at a low voltage, and in which the occurrence of a crosstalk phenomenon is suppressed. Provided is an optical modulator including a substrate 1 having an electro-optic effect, and an optical waveguide 10 and a control electrode that are formed on the substrate, in which the optical waveguide has a structure in which a plurality of Mach-Zehnder type optical waveguides are disposed in parallel, the control electrode has a GSSG type differential electrode structure in which two signal electrodes S are disposed between two ground electrodes G for one of the Mach-Zehnder type optical waveguides, and a crosstalk suppressing unit that suppresses signal crosstalk is provided in the ground electrode sandwiched between adjacent Mach-Zehnder type optical waveguides, so that optical modulator can be driven at a low voltage, and in which the occurrence of a crosstalk phenomenon is suppressed.

Abstract: In an optical waveguide device having a plurality of intersections between a convex optical waveguide and a signal electrode, the generation of disturbance modulation at the intersections is effectively reduced, thereby achieving good operating characteristics. An optical waveguide device includes a substrate on which an optical waveguide is formed, an intermediate layer formed on the substrate, and a signal electrode and a ground electrode formed on the intermediate layer, in which the optical waveguide includes a protruding portion extending on the substrate, the signal electrode has an action portion that extends along the optical waveguide and controls a light wave propagating through the optical waveguide, and an intersection that crosses over the optical waveguide, and the intermediate layer is formed such that a thickness at the intersection is thicker than a thickness at the action portion.

Abstract: In order to provide an optical modulator capable of preventing damage to the substrate and preventing deterioration of the properties of the modulator by reducing the stress on the substrate generated by the modulation electrode, there is provided an optical modulator 1, including: a substrate 5 having an electro-optic effect; an optical waveguide 10 formed on the substrate 5; and a modulation electrode (signal electrode S and ground electrode G) provided on the substrate 5 and modulating a light wave propagating in the optical waveguide 10, wherein a resin 8 to reduce the stress on the substrate 5 generated by the modulation electrode is arranged between a part of the bottom surface of the modulation electrode and the substrate 5 facing a part of the bottom surface of the modulation electrode.

Abstract: In an optical modulation element using a thinly processed substrate, cracking of the substrate during electrical connection is prevented, and poor connection or a reduction in manufacturing yield is prevented. An optical waveguide element includes an optical substrate on which an optical waveguide and a conductor pattern are formed, and a support substrate that supports the optical substrate, in which the conductor pattern includes at least one electrical connection area defined as a range in which electrical connection is performed, the optical substrate has a substrate removal portion in which a material of the optical substrate has been removed to penetrate through the optical substrate at a portion corresponding to the electrical connection area, and at least a part of the electrical connection area is formed on the support substrate via the substrate removal portion.

Abstract: Provided is an optical waveguide element that prevents leaked light generated at a forking section from entering a downstream optical waveguide such as another forking section, thereby affording minimal degradation of optical characteristics. The optical waveguide is characterized in that: at least one of two fork waveguides (20a, 20b) forking from a first forking section (20) comprises a second forking section (21, 22); slab waveguides (3c-1 to 3c-3) are formed between the two fork waveguides; and between the first forking section and the second forking section, slits (41, 42) are formed that partition the slab waveguides into a first slab waveguide area (3c-1) close to the first forking section and second slab waveguide areas (3c-2, 3c-3) close to the second forking section(s).

Abstract: An optical waveguide device including: an optical waveguide composed of a protruding portion extending on a substrate; a signal electrode that is formed on the substrate and controls light waves propagating through the optical waveguide, in which the optical waveguide includes a Mach-Zehnder optical waveguide including two parallel waveguides having curved portions, the signal electrode includes two signal lines for transmitting a differential signal, respectively intersecting the two parallel waveguides at the curved portions, and in an intersection region, which is a region on the substrate where the two signal lines and the two parallel waveguides intersect, at least one of the two signal lines has a signal propagation velocity faster than in a portion other than the intersection region or one of the two signal lines has a signal propagation velocity faster than an other signal line.

Abstract: A method of roughening the upper surface of the slab waveguide includes a method of locally forming roughness using an electron beam and a method of roughening the upper surface via etching. As an etching condition for the rough surface, processing is performed under a condition in which roughness is generated compared to a processing condition for the rib top portion. Particularly, since the surface can be simply locally roughened by etching, the rough surface can be formed much more simply than that of the unnecessary light beam removing unit in Patent Literature No. 1. Roughness of the rough surface is preferably 10 nm or larger in arithmetic average roughness Ra.

Abstract: The purpose of the present invention is to provide an optical modulator in which propagation loss related to transmission of a high-frequency signal is reduced. An optical modulator, in which an electro-optical conversion element E/OC and a driver circuit DRV for driving the electro-optical conversion element are housed in the same case CA, includes: a multiplexer MUX that converts an input modulation signal, which is input from an outside of the case, into an output modulation signal having a higher frequency than the input modulation signal, and supplies the output modulation signal to the driver circuit, in which the multiplexer is housed in the case CA.

Abstract: In an optical waveguide device having a plurality of intersections between a convex optical waveguide and a signal electrode, the occurrence of disturbance modulation at the intersections is effectively reduced, thereby achieving good operating characteristics. The optical waveguide device includes an optical waveguide composed of a protruding portion extending on the substrate, and a signal electrode formed on the substrate and controlling a light wave propagating through the optical waveguide. The optical waveguide includes a Mach-Zehnder optical waveguide including two parallel waveguides having a curved portions, the signal electrode includes two signal lines intersecting the two parallel waveguides at the curved portions and transmitting a differential signal, and each of the two signal lines is configured such that the intersection lengths on the two parallel waveguides are the same as each other.

Abstract: An optical modulator includes an optical waveguide device including an optical waveguide and a signal electrode for controlling a light wave propagating through the optical waveguide, a drive circuit that outputs two high-frequency signals, and two termination resistors for respectively terminating the two high-frequency signals, in which one high-frequency signal among the high-frequency signals output from the drive circuit propagates through the signal electrode of the optical waveguide device and is terminated by a first termination resistor that is one of the termination resistors, an other high-frequency signal among the high-frequency signals output from the drive circuit is terminated by a second termination resistor that is an other one of the termination resistors, a resistance value of the first termination resistor is lower than a resistance value of the second termination resistor, and the signal electrode includes a plurality of sections having constant impedances different from each other.

Abstract: An optical modulator includes a relay substrate having signal conductor patterns that connect signal input terminals and signal electrodes of an optical modulation element and ground conductor patterns, and a housing, in which the signal conductor pattern includes a component mounting portion including an electrical circuit element. Two ground conductor patterns sandwiching the signal conductor pattern are formed in an asymmetrical shape in a plan view within a component mounting area having a square shape in the plan view centered on the component mounting portion. A direction of a side of the component mounting area having the square shape is same as the extending direction of the signal conductor pattern and a length of a side of the component mounting area is equal to a distance from a center of the component mounting portion to a portion on an adjacent signal conductor pattern closest to the center.

Abstract: Provided is an optical modulator that can be driven at lower voltage through the use of differential signal output. An optical modulator includes a substrate 1 and optical waveguides (21, 22) and a control electrode that are formed on the substrate, in which the optical waveguide includes Mach-Zehnder type optical waveguide, the control electrode is provided with two ground electrodes sandwiching three signal electrodes; the three signal electrodes are constituted by second and third signal electrodes that sandwich a first signal electrode, and have a wiring structure in which one modulation signal of the differential signal is applied to the first signal electrode, and the other modulation signal of the differential signal is applied to the second and third signal electrodes; and one branched waveguide (21) out of two Mach-Zehnder type optical waveguides is disposed between the first and second signal electrodes, and the other branched waveguide (22) is disposed between the first and third signal electrodes.

Abstract: An optical modulation element that can be housed in the same housing together with an electronic circuit is implemented without deteriorating the high-frequency characteristics and the optical modulation characteristics and without increasing a size of the housing.

Abstract: The optical absorption loss of the optical waveguide and the signal propagation loss of the high-frequency signal electrode are both reduced at a plurality of intersections between the convex optical waveguide and the high-frequency signal electrode, thereby achieving good operating characteristics. An optical waveguide device includes a substrate on which optical waveguides are formed, and an electrode that is formed on the substrate and has intersections crossing over the optical waveguides, in which the optical waveguides are configured by protruding portions extending on the substrate, and an intermediate layer made of a resin is provided at the adjacent intersections along the electrode to fill spaces between the protruding portions along the electrode and covers top of the protruding portions.

Abstract: It is possible to provide an optical modulator in which a transmission loss from a driver circuit element to a modulation substrate is reduced. An optical modulator includes a modulation substrate (1) that includes an optical waveguide (200) and a modulation electrode (10) for modulating a light wave propagating through the optical waveguide, a driver circuit element (2) that generates a modulation signal to be applied to the modulation electrode (10), and a case (3) that accommodates the modulation substrate (1) and the driver circuit element (2), in which an output terminal (20?) that outputs the modulation signal is provided on an upper surface side of the driver circuit element (2), and a wiring substrate (4) including a wiring that electrically connects the output terminal (20?) and the modulation electrode (10) is disposed above the driver circuit element (2) and the modulation substrate (1) to straddle both the driver circuit element (2) and the modulation substrate (1).