Abstract: A high-frequency transmission line is provided that improves a high-frequency characteristic. The high-frequency transmission line includes a first conductor line, a termination resistance connected to the first conductor line, a second conductor line connected to the termination resistance, and a ground line that is provided to be opposed to the first conductor line, the termination resistance, and the second conductor line to have a predetermined distance thereto and that is connected to the second conductor line. The first conductor line and the ground line are formed to have a line width decreasing toward the termination resistance, respectively.

Abstract: An IQ optical modulator including: a parent Mach-Zehnder type (MZM) optical waveguide; child MZM optical waveguides constituting two arms of the parent MZM; two electrode transmission lines provided along the two arms of the child MZM, respectively, and receiving modulation signal to phase-modulate an optical signal; an RF extension line connected to the two electrode transmission lines, respectively; a first optical splitter branching light into the two arms of the parent MZM; a second optical splitter branching light into the two arms of the child MZM; and a first optical multiplexer multiplexing light from the two arms of the child MZM, wherein stripe direction of the child MZM optical waveguide is same as the RF extension line, the second optical splitter, and the first optical multiplexer, and is orthogonal to the first optical splitter.

Abstract: An IQ optical modulator including: a parent Mach-Zehnder type (MZM) optical waveguide; child MZM optical waveguides constituting two arms of the parent MZM; two electrode transmission lines provided along the two arms of the child MZM, respectively, and receiving modulation signal to phase-modulate an optical signal; an RF extension line connected to the two electrode transmission lines, respectively; a first optical splitter branching light into the two arms of the parent MZM; a second optical splitter branching light into the two arms of the child MZM; and a first optical multiplexer multiplexing light from the two arms of the child MZM, wherein stripe direction of the child MZM optical waveguide is same as the RF extension line, the second optical splitter, and the first optical multiplexer, and is orthogonal to the first optical splitter.

Abstract: This invention provides a high-frequency line adopting a structure to suppress an impedance variation and occurrence of an excessive power loss in high-frequency wiring having intersection with an optical waveguide. A high-frequency line is a microstrip line which has a basic configuration of stacking a ground electrode, a dielectric layer, and a signal electrode in this order on a SI-InP substrate. In addition, as shown in a transverse sectional view, an optical waveguide core made of InP-based semiconductor intersects with the high-frequency line in a crossing manner. A width of the signal electrode is partially increased in a certain region covering the intersection with the optical waveguide along a propagating direction of the high-frequency line. In the microstrip line, the width of the signal electrode is partially increased from w1 to w2, and characteristic impedance is thus reduced as compared to one with the uniform width w1.

Abstract: To provide a Mach-Zehnder (MZ) type semiconductor optical modulation element that can be used as a modulator, which is ultrafast and excellent in electrical stability. A semiconductor optical modulation element of a Mach-Zehnder type that performs modulation of light using a refractive index modulation region where a refractive index of the light guided to an optical waveguide is modulated and an input and output region where multiplexing/demultiplexing of the light split in the refractive index modulation region is performed, characterized in that in the refractive index modulation region of the optical waveguide, an n-type clad layer, an i core layer, and a p-type clad layer are stacked in the order from a top layer on a substrate surface equivalent to a (100) plane of a sphalerite-type seminsulating semiconductor crystal substrate, the n-type clad layer is formed in a ridge shape in an inverted mesa direction, and a capacitancl-oaded electrode is provided on the n-type clad layer.

Abstract: This invention provides a high-frequency line adopting a structure to suppress an impedance variation and occurrence of an excessive power loss in high-frequency wiring having intersection with an optical waveguide. A high-frequency line is a microstrip line which has a basic configuration of stacking a ground electrode, a dielectric layer, and a signal electrode in this order on a SI-InP substrate. In addition, as shown in a transverse sectional view, an optical waveguide core made of InP-based semiconductor intersects with the high-frequency line in a crossing manner. A width of the signal electrode is partially increased in a certain region covering the intersection with the optical waveguide along a propagating direction of the high-frequency line. In the microstrip line, the width of the signal electrode is partially increased from w1 to w2, and characteristic impedance is thus reduced as compared to one with the uniform width w1.

Abstract: To provide a Mach-Zehnder (MZ) type semiconductor optical modulation element that can be used as a modulator, which is ultrafast and excellent in electrical stability. A semiconductor optical modulation element of a Mach-Zehnder type that performs modulation of light using a refractive index modulation region where a refractive index of the light guided to an optical waveguide is modulated and an input and output region where multiplexing/demultiplexing of the light split in the refractive index modulation region is performed, characterized in that in the refractive index modulation region of the optical waveguide, an n-type clad layer, an i core layer, and a p-type clad layer are stacked in the order from a top layer on a substrate surface equivalent to a (100) plane of a sphalerite-type semi-insulating semiconductor crystal substrate, the n-type clad layer is formed in a ridge shape in an inverted mesa direction, and a capacitance-loaded electrode is provided on the n-type clad layer.

Abstract: A high-frequency transmission line is provided that improves a high-frequency characteristic. The high-frequency transmission line includes a first conductor line, a termination resistance connected to the first conductor line, a second conductor line connected to the termination resistance, and a ground line that is provided to be opposed to the first conductor line, the termination resistance, and the second conductor line to have a predetermined distance thereto and that is connected to the second conductor line. The first conductor line and the ground line are formed to have a line width decreasing toward the termination resistance, respectively.