Abstract: A Mach-Zehnder modulator includes an optical waveguide, first and second arm waveguides, an embedded area, an conductive semiconductor layer, first and second signal upper layers extending over the embedded area and connected to the first and second arm waveguides, a first ground upper layer extending over the embedded area along at least one of the first and the second signal upper layers, a ground lower layer connected to the first ground upper layer and extending through the embedded area along the and second first signal upper layers, and a first conductive upper layer connected to the ground lower layer and extending over the embedded area along at least one of the first and second signal upper layers. The ground lower layer extends between the optical waveguide, the first signal upper layer, and the second signal upper layer.

Abstract: A Mach-Zehnder modulator includes: first and second resistive elements each having first and second contact areas, the first and second contact areas of the second resistive element being arranged in a direction of a first axis, the first and second contact areas of the second resistive element being arranged in a direction of a second axis; a common conductor connecting the first contact areas of the first and second resistive elements with each other; first and second waveguide structures each including a waveguide portion extending in a direction of a third axis intersecting the first and second axes; a first signal conductor connected to the waveguide portion of the first waveguide structure and the second contact area of the first resistive element; and a second signal conductor connected to the waveguide portion of the second waveguide structure and the second contact area of the second resistive element.

Abstract: A spot-size converter includes: a support body that includes a main surface including a first to a fifth areas; a mesa structure that includes a first part on the first area and includes a second part on the second to the fourth areas; and an embedding structure that includes a first region and a second region in which a first and a second side-surfaces of the second part of the mesa structure are respectively embedded. The second part of the mesa structure includes a portion that has a width gradually decreasing in a direction from the third area toward the fifth area. The first region of the embedding structure extends along the first side-surface and terminates at one of the third and the fourth areas. The second region of the embedding structure extends along the second side-surface of the second part and is disposed on the fifth area.

Abstract: A Mach-Zehnder modulator includes an optical waveguide, first and second arm waveguides, an embedded area, an conductive semiconductor layer, first and second signal upper layers extending over the embedded area and connected to the first and second arm waveguides, a first ground upper layer extending over the embedded area along at least one of the first and the second signal upper layers, a ground lower layer connected to the first ground upper layer and extending through the embedded area along the and second first signal upper layers, and a first conductive upper layer connected to the ground lower layer and extending over the embedded area along at least one of the first and second signal upper layers. The ground lower layer extends between the optical waveguide, the first signal upper layer, and the second signal upper layer.

Abstract: A Mach-Zehnder modulator includes: a first arm waveguide having first to third waveguide portions, the third waveguide portion being curved to couple the first and second waveguide portions with each other; a second arm waveguide having first to third waveguide portions, the third waveguide portion being curved to couple the first and second waveguide portions with each other, and a differential signal conductor having first and second signal conductors for driving the first and second arm waveguides, respectively. The first signal conductor has a first conductor portion and a first intersecting conductor portion connected thereto. The second signal conductor has a first conductor portion and a second intersecting conductor portion connected thereto. One of the first and second intersecting conductor portions includes an upper conducting layer, and the other includes a lower conducting layer. The upper conducting layer extends on the lower conducting layer apart therefrom.

Abstract: A Mach-Zehnder modulator includes: a first arm waveguide having first to third waveguide portions, the third waveguide portion being curved to couple the first and second waveguide portions with each other; a second arm waveguide having first to third waveguide portions, the third waveguide portion being curved to couple the first and second waveguide portions with each other, and a differential signal conductor having first and second signal conductors for driving the first and second arm waveguides, respectively. The first signal conductor has a first conductor portion and a first intersecting conductor portion connected thereto. The second signal conductor has a first conductor portion and a second intersecting conductor portion connected thereto. One of the first and second intersecting conductor portions includes an upper conducting layer, and the other includes a lower conducting layer. The upper conducting layer extends on the lower conducting layer apart therefrom.

Abstract: A Mach-Zehnder modulator includes: a first semiconductor arm including a lower semiconductor region, an upper semiconductor layer, and a core layer disposed between the lower semiconductor region and the upper semiconductor layer; a second semiconductor arm including a lower semiconductor region, an upper semiconductor layer, and a core layer disposed between the lower semiconductor region and the upper semiconductor layer; a conductive semiconductor region connecting the lower semiconductor regions of the first and second semiconductor arms with each other; and a differential transmission line including a first signal transmitting conductor, a second signal transmitting conductor, and a reference potential conductor. The first and second signal transmitting conductors are coupled to the first and second semiconductor arms, respectively.

Abstract: A semiconductor optical modulator includes an input waveguide provided on a side of a substrate, a first and a second output waveguides provided on the same side of the substrate, a dividing portion optically connected to the input waveguide, eight arm waveguides optically connected to the dividing portion, a first multiplexing portion optically connecting four of the arm waveguides to the first output waveguide, a second multiplexing portion optically connecting the other four of the arm waveguides to the second output waveguide, and modulation electrodes provided on respective ones of the eight arm waveguides. The first and second output waveguides are arranged symmetrically about the input waveguide.

Abstract: A spot size converter includes: a first semiconductor waveguide structure having a first width enabling single mode propagation; a second semiconductor waveguide structure having a second width greater than the first width, a second semiconductor waveguide structure including an end face for optically coupling with an external waveguide; a third semiconductor waveguide structure having a third width greater than the first and second widths, the third semiconductor waveguide structure being optically coupled to the second semiconductor waveguide structure; and a single tapered waveguide having a first end portion connected to the third semiconductor waveguide structure, and a second end portion connected to the first semiconductor waveguide structure, the single tapered waveguide having a width gradually changing in a direction from the first end portion to the second end portion.

Abstract: A Mach-Zehnder modulator includes: a support having a principal surface, the principal surface having a first area, a second area, and a third area; a first structure including first and second semiconductor mesas disposed on the first and second areas, respectively; a second structure including a first strip-shaped semiconductor region on the second area, a second strip-shaped semiconductor region on the third area, and a first strip-shaped void and a second strip-shaped void defining the first and second strip-shaped semiconductor regions; a first electrode disposed on the first semiconductor mesa in the first area, the first strip-shaped semiconductor region of the second structure being disposed between the support and the second semiconductor mesa of the first structure in the second area, and the first and second semiconductor mesas, and the first and second strip-shaped semiconductor regions being arranged to constitute a first arm waveguide of the Mach-Zehnder modulator.

Abstract: A Mach-Zehnder modulator includes: a support having a principal surface, the principal surface having a first area, a second area, and a third area; a first structure including first and second semiconductor mesas disposed on the first and second areas, respectively; a second structure including a first strip-shaped semiconductor region on the second area, a second strip-shaped semiconductor region on the third area, and a first strip-shaped void and a second strip-shaped void defining the first and second strip-shaped semiconductor regions; a first electrode disposed on the first semiconductor mesa in the first area, the first strip-shaped semiconductor region of the second structure being disposed between the support and the second semiconductor mesa of the first structure in the second area, and the first and second semiconductor mesas, and the first and second strip-shaped semiconductor regions being arranged to constitute a first arm waveguide of the Mach-Zehnder modulator.

Abstract: A spot size converter includes: a first semiconductor waveguide structure having a first width enabling single mode propagation; a second semiconductor waveguide structure having a second width greater than the first width, a second semiconductor waveguide structure including an end face for optically coupling with an external waveguide; a third semiconductor waveguide structure having a third width greater than the first and second widths, the third semiconductor waveguide structure being optically coupled to the second semiconductor waveguide structure; and a single tapered waveguide having a first end portion connected to the third semiconductor waveguide structure, and a second end portion connected to the first semiconductor waveguide structure, the single tapered waveguide having a width gradually changing in a direction from the first end portion to the second end portion.

Abstract: A modulator including: a Mach-Zehnder modulator that includes an optical waveguide disposed on a substrate, the optical waveguide including an electrode thereon; a resin layer disposed on the substrate, the resin layer embedding the optical waveguide, the resin layer having a groove arranged besides the optical waveguide; a termination resistor disposed on the substrate in the groove of the resin layer; and a first wiring disposed on the resin layer, the first wiring being connected to the termination resistor and the electrode of the optical waveguide.

Abstract: An optical semiconductor device including: a substrate having a principal surface; first and second optical waveguides disposed on the principal surface of the substrate, the first and second optical waveguides extending in a first direction, the second optical waveguide being arranged adjacent to the first optical waveguide in a second direction intersecting with the first direction; first and second signal electrodes disposed on the first and second optical waveguides; a resistor disposed on the principal surface, the resistor being arranged between the first optical waveguide and the second optical waveguide, the resistor being electrically connected to the first signal electrode and the second signal electrode; a resin layer disposed on the principal surface, top surfaces of the first and second signal electrodes, and the resistor; and a capacitor disposed on the resin layer, the capacitor being electrically connected to the resistor through an opening of the resin layer.

Abstract: A Mach-Zehnder modulator includes: a conductive semiconductor region disposed on a substrate; a first waveguide arm disposed on the conductive semiconductor region; a second waveguide arm disposed on the conductive semiconductor region; a first electrode disposed on the first waveguide arm, the first electrode receiving a first drive signal applied to the first waveguide arm; a second electrode disposed on the second waveguide arm, the second electrode receiving a second drive signal applied to the second waveguide arm; a first ground electrode disposed on the conductive semiconductor region, the first ground electrode being electrically connected to a reference potential; and a second ground electrode disposed on the conductive semiconductor region. The first and second drive signals constitute a differential signal. The second ground electrode is electrically connected to the first ground electrode via the conductive semiconductor region.

Abstract: A semiconductor optical device including: a substrate including a first region and a second region; a first optical waveguide disposed on the first region, the first optical waveguide including a core layer and a cladding layer disposed on the core layer, the cladding layer including a first cladding region and a semiconductor layer disposed on the first cladding region, the first optical waveguide extending from an end facet of the semiconductor optical device to a boundary between the first region and the second region; a second optical waveguide disposed on the second region; and a region disposed on the cladding layer, the region having a lower refractive index than that of the first cladding region. The semiconductor layer has a higher refractive index than that of the first cladding region. The thickness of the core layer monotonically increases from the end facet toward the boundary.

Abstract: A Mach-Zehnder modulator includes: a conductive semiconductor region disposed on a substrate; a first waveguide arm disposed on the conductive semiconductor region; a second waveguide arm disposed on the conductive semiconductor region; a first electrode disposed on the first waveguide arm, the first electrode receiving a first drive signal applied to the first waveguide arm; a second electrode disposed on the second waveguide arm, the second electrode receiving a second drive signal applied to the second waveguide arm; a first ground electrode disposed on the conductive semiconductor region, the first ground electrode being electrically connected to a reference potential; and a second ground electrode disposed on the conductive semiconductor region. The first and second drive signals constitute a differential signal. The second ground electrode is electrically connected to the first ground electrode via the conductive semiconductor region.

Abstract: A method for manufacturing a semiconductor optical waveguide device includes the steps of forming a waveguide mesa having first and second portions by etching a stacked semiconductor layer through a first mask; forming a dummy buried region embedding a top surface and side surfaces of the waveguide mesa; forming a second mask on the dummy buried region, the second mask having an opening on the first portion and having a pattern on the second portion; forming a third mask having an opening that reaches a top surface of the first portion, the third mask including a dummy buried mask formed by etching the dummy buried region through the second mask; forming an upper mesa by etching the waveguide mesa through the third mask; and after removing the third mask, forming a lower mesa by etching the stacked semiconductor layer, the lower mesa having a greater width than that of the upper mesa.

Abstract: A semiconductor optical device including: a substrate including a first region and a second region; a first optical waveguide disposed on the first region, the first optical waveguide including a core layer and a cladding layer disposed on the core layer, the cladding layer including a first cladding region and a semiconductor layer disposed on the first cladding region, the first optical waveguide extending from an end facet of the semiconductor optical device to a boundary between the first region and the second region; a second optical waveguide disposed on the second region; and a region disposed on the cladding layer, the region having a lower refractive index than that of the first cladding region. The semiconductor layer has a higher refractive index than that of the first cladding region. The thickness of the core layer monotonically increases from the end facet toward the boundary.

Abstract: An optical semiconductor device including: a substrate having a principal surface; a first and a second optical waveguides disposed on the principal surface of the substrate, the first and second optical waveguides extending in a first direction, the second optical waveguide being arranged adjacent to the first optical waveguide in a second direction intersecting with the first direction; a first and a second signal electrodes disposed on the first and second optical waveguides; a resistor disposed on the principal surface, the resistor being arranged between the first optical waveguide and the second optical waveguide, the resistor being electrically connected to the first signal electrode and the second signal electrode; a resin layer disposed on the principal surface, top surfaces of the first and second signal electrodes, and the resistor; and a capacitor disposed on the resin layer, the capacitor being electrically connected to the resistor through an opening of the resin layer.