Light polarisation converter and method of manufacture

A photonic integrated circuit comprising a light polarisation converter comprising:

• a first layer comprising a first surface and a second surface, the second surface offset from the first surface along a first axis and a second axis, the first axis perpendicular to the first surface, and the second axis parallel to the first surface;
• a second layer;
• and
• a waveguide between, and in contact with each of, the first layer and the second layer, the waveguide comprising:
• a first waveguide portion in contact with the first surface, the first waveguide portion having a first thickness different to a second thickness of the first waveguide portion, the first thickness and the second thickness perpendicular the first surface, and
• a second waveguide portion in contact with the second surface, such that the second waveguide portion is offset from the first waveguide portion.

A method of manufacturing a light polarisation converter comprising:

• at least partly forming a first layer using a precursor to the first layer, the first layer comprising a first surface and a second surface, the second surface offset from the first surface along a first axis and a second axis, the first axis perpendicular to the first surface, and the second axis parallel to the first surface;
• at least partly forming a waveguide using a precursor to the waveguide, the waveguide on and in contact with the first layer, the waveguide comprising:
• a first waveguide portion in contact with the first surface, and a second waveguide portion in contact with the second surface, a first thickness of the first waveguide portion different to a second thickness of the first waveguide portion, the first thickness and the second thickness perpendicular to the first surface;
• and
• at least partly forming a second layer, using a precursor to the second layer, the second layer on and in contact with the waveguide, the waveguide between the first layer and the second layer.