Optical structure

An optical structure comprising:

• a 1 to 1 multimode interference waveguide section, the multimode interference waveguide section comprising an input face, an output face and sidewalls extending therebetween, the sidewalls extending substantially parallel to a length axis;
• a single input optical waveguide abutting the input face and spaced apart from the sidewalls;
• the single input optical waveguide being at least one of inclined to the length axis and arranged closer to one sidewall than the other;
• a single output optical waveguide abutting the output face and spaced apart from the sidewalls;
• the input face being divided into first and second input face shoulder portions arranged on opposite sides of the input optical waveguide;
• and
• the output face being divided into first and second output face shoulder portions arranged on opposite sides of the output optical waveguide;
• the optical structure further comprising at least one external reflector appendage, the at least one external reflector appendage comprising a reflector portion integrally extending from a shoulder portion and an appendage waveguide integrally extending from the reflector portion along an axis inclined to the length axis, the reflector portion comprising a reflector wall arranged such that light travelling parallel to the length axis which is incident on the reflector wall is reflected into the appendage waveguide.