Optical modulator element, optical transmitter, and optical transceiver

An optical transmitter comprising an optical modulator element that includes, on a substrate, an optical branching portion and an optical multiplexing portion each of which includes a first material, two optical waveguide arms each of which connects the optical branching portion and the optical multiplexing portion, and electrodes that apply an electrical signal to the two optical waveguide arms, wherein

• each of optical waveguides of the two optical waveguide arms includes
• a first optical waveguide that includes the first material,
• a second optical waveguide that includes a second material that has a higher electro-optical effect than the first material, and
• a transition portion that performs an optical transition between the first optical waveguide and the second optical waveguide, and
• the substrate includes a hollow portion in which all or a part of the substrate located below the second optical waveguide in a plan view has been removed.

An optical transceiver comprising:

• an optical modulator element that includes an optical modulator;
• an optical receiver element that includes an optical receiver;
• and
• a processor that executes signal processing on the optical modulator and the optical receiver, wherein
• the optical modulator element includes, on a substrate,
• an optical branching portion and an optical multiplexing portion each of which includes a first material,
• two optical waveguide arms each of which connects the optical branching portion and the optical multiplexing portion, and
• electrodes that apply an electrical signal to the two optical waveguide arms,
• each of optical waveguides of the two optical waveguide arms includes
• a first optical waveguide that includes the first material,
• a second optical waveguide that includes a second material that has a higher electro-optical effect than the first material, and
• a transition portion that performs an optical transition between the first optical waveguide and the second optical waveguide, and
• the substrate includes a hollow portion in which all or a part of the substrate located below the second optical waveguide in a plan view has been removed.