Polarization control device

A polarization control device comprising:

• a multi-mode interference device having a primary-side end face including a first port and a second port, a secondary-side end face including a port, a first side face, and a second side face;
• a first phase shifter optically coupled to the first port in the primary-side end face of the multi-mode interference device;
• a first optical waveguide optically coupled via the first phase shifter to the first port in the primary-side end face of the multi-mode interference device;
• a second optical waveguide optically coupled to the second port in the primary-side end face of the multi-mode interference device;
• a tapered waveguide having one end and an other end, the one end being optically coupled to the port in the secondary-side end face of the multi-mode interference device;
• and
• an input optical waveguide configured to supply input light containing transverse electric polarized light and/or traverse magnetic polarized light to the multi-mode interference device, the input optical waveguide being optically coupled via the tapered waveguide to the port in the secondary-side end face of the multi-mode interference device, wherein
• the first port in the primary-side end face and the second port in the primary-side end face are located on a first axis and a second axis, respectively, in the primary-side end face,
• the port in the secondary-side end face is located on a third axis in the secondary-side end face, the third axis being located between the first axis and the second axis,
• the first axis, the second axis, and the third axis extend in a direction from the primary-side end face to the secondary-side end face of the multi-mode interference device, and
• the tapered waveguide has a width decreasing in a direction from the one end to the e other end of the tapered waveguide.