Optical control device

An optical control device, comprising:

• a substrate;
• first and second optical waveguides provided on the substrate, and extending along a main surface of the substrate;
• a first control signal electrode provided on the main surface of the substrate so as to change a refractive index of light propagating through the inside of the first optical waveguide on the basis of a first electrical signal supplied from an outer side, the first control signal electrode including a first operating electrode part extending along the first optical waveguide to apply an electrical field to the first optical waveguide, and a first input-side signal electrode extending along the main surface of the substrate to transmit the first electrical signal to the first operating electrode part;
• a second control signal electrode provided on the main surface of the substrate so as to change a refractive index of light propagating through the inside of the second optical waveguide on the basis of a second electrical signal supplied from an outer side, the second control signal electrode including a second operating electrode part extending along the second optical waveguide to apply an electrical field to the second optical waveguide, and a second input-side signal electrode extending along the main surface of the substrate to transmit the second electrical signal to the second operating electrode part;
• an inter-signal-electrode ground electrode provided on the main surface of the substrate between the first input-side signal electrode and the second input-side signal electrode, the inter-signal-electrode ground electrode being positioned to be spaced away from the first input-side signal electrode and the second input-side signal electrode in a plan view;
• a first ground electrode provided on the main surface of the substrate on a side opposite to an inter-signal-electrode ground electrode side with the first input-side signal electrode interposed between the first ground electrode and the inter-signal-electrode ground electrode, the first ground electrode being positioned to be spaced away from the first input-side signal electrode in a plan view;
• and
• a second ground electrode provided on the main surface of the substrate on a side opposite to an inter-signal-electrode ground electrode side with the second input-side signal electrode interposed between the second ground electrode and the inter-signal-electrode ground electrode, the second ground electrode being positioned to be spaced away from the second input-side signal electrode in a plan view,
• wherein, in a plan view, the substrate includes a first groove provided between the first input-side signal electrode and the inter-signal-electrode ground electrode, a second groove provided between the first input-side signal electrode and the first ground electrode, a third groove provided between the second input-side signal electrode and the inter-signal-electrode ground electrode, and a fourth groove provided between the second input-side signal electrode and the second ground electrode,
• one end of the first ground electrode, one end of the first input-side signal electrode, one end of the inter-signal-electrode ground electrode, one end of the second input-side signal electrode, and one end of the second ground electrode are arranged along a first direction along the main surface of the substrate in this order, and
• when a spaced distance between the one end of the first input-side signal electrode and the one end of the second input-side signal electrode along the first direction is set as D, and a spaced distance between the one end of the first ground electrode and the one end of the inter-signal-electrode ground electrode along the first direction or a spaced distance between the one end of the second ground electrode and the one end of the inter-signal-electrode ground electrode along the first direction is set as K, a value of D/K is 3.0 or less.