Mach-Zehnder modulator, method of making optical waveguide structure

A Mach-Zehnder modulator comprising:

• a conductive, semiconductor region provided on a primary surface of a substrate;
• a first semiconductor structure provided on the conductive semiconductor region, the first semiconductor structure including an optical branching coupler and a part of a first arm semiconductor waveguide;
• a second semiconductor structure provided on the conductive semiconductor region, the second semiconductor structure including a part of the first arm semiconductor waveguide;
• and
• a third semiconductor structure provided on the conductive semiconductor region, the third semiconductor structure including a part of the first arm semiconductor waveguide,
• the primary surface having first to third areas, the first to third areas being arranged sequentially in a waveguide axis, the first to third semiconductor structures being provided on the first to third areas, respectively,
• the first semiconductor structure including a semiconductor laminate, the semiconductor laminate including a first cladding layer, a core layer and a second cladding layer, the first cladding layer, the core layer and the second cladding layer being arranged in a direction normal to the primary surface of the substrate,
• the second semiconductor structure including the semiconductor laminate and a first contact portion provided on a top of the semiconductor laminate,
• the third semiconductor structure including the semiconductor laminate and a second contact portion provided on the top of the semiconductor laminate,
• the first contact portion and the second contact portion constituting a contact layer,
• the second semiconductor structure having first and second waveguide sides of the first arm semiconductor waveguide,
• the first contact portion of the second semiconductor structure having an edge,
• the edge terminating the contact layer,
• the edge extending in a direction of a first reference plane on the top of the semiconductor laminate to reach the first waveguide side,
• the first reference plane and a top of the second semiconductor structure intersecting with each other to define a line of intersection obliquely-crossed with an upper edge of the first waveguide side at a first angle that is different from a right angle,
• the edge extending in a direction of a second reference plane on the top of the semiconductor laminate to reach the second waveguide side, and
• the second reference plane and the top of the second semiconductor structure intersecting with each other to define a line of intersection obliquely-crossed with an upper edge of the second waveguide side at a second angle that is different from a right angle,
• wherein an electrode is in contact with the conductive semiconductor region in the third area.

A Mach-Zehnder modulator comprising:

• a conductive semiconductor region provided on a primary surface of a substrate;
• a first semiconductor structure provided on the conductive semiconductor region, the first semiconductor structure including an optical branching coupler and a part of a first arm semiconductor waveguide;
• a second semiconductor structure provided on the conductive semiconductor region, the second semiconductor structure including a part of the first arm semiconductor waveguide;
• and
• a third semiconductor structure provided on the conductive semiconductor region, the third semiconductor structure including a part of the first arm semiconductor waveguide,
• the primary surface having first to third areas, the first to third areas being arranged sequentially in a waveguide axis, the first to third semiconductor structures being provided on the first to third areas, respectively,
• the first semiconductor structure including a semiconductor laminate, the semiconductor laminate including a first cladding layer, a core layer and a second cladding layer, the first cladding layer, the core layer and the second cladding layer being arranged in a direction normal to the primary surface of the substrate,
• the second semiconductor structure including the semiconductor laminate and a first contact portion provided on a top of the semiconductor laminate,
• the third semiconductor structure including the semiconductor laminate and a second contact portion provided on the top of the semiconductor laminate,
• the first contact portion and the second contact portion constituting a contact layer,
• the second semiconductor structure having first and second waveguide sides of the first arm semiconductor waveguide,
• the first contact portion of the second semiconductor structure having an edge,
• the edge terminating the contact layer,
• the edge extending in a direction of a first reference plane on the top of the semiconductor laminate to reach the first waveguide side,
• the first reference plane and a top of the second semiconductor structure intersecting with each other to define a line of intersection obliquely-crossed with an upper edge of the first waveguide side at a first angle that is different from a right angle,
• the edge extending in a direction of a second reference plane on the top of the semiconductor laminate to reach the second waveguide side,
• the second reference plane and the top of the second semiconductor structure intersecting with each other to define a line of intersection obliquely-crossed with an upper edge of the second waveguide side at a second angle that is different from a right angle,
• the first semiconductor structure, the second semiconductor structure and the third semiconductor structure further include respective parts of a second arm semiconductor waveguide,
• the second arm semiconductor waveguide includes another semiconductor laminate, and
• the Mach-Zehnder modulator further comprises first to fourth terraces, the first to fourth terraces are disposed in the second and third areas, the first terrace is obliquely-connected with a bottom edge of the first waveguide side of the first arm semiconductor waveguide, the second terrace is obliquely-connected with a bottom edge of the second waveguide side of the first arm semiconductor waveguide, the third terrace is obliquely-connected with a bottom edge of a first waveguide side of the second arm semiconductor waveguide, and the second terrace is obliquely-connected with a bottom edge of a second waveguide side of the second arm semiconductor waveguide.