Patent ID: 9366820
Filing Date: 2016-06-14
CPC Classification: G02B,H04B

Claim Text:
1. A coherent mixer comprising: optical inputs; optical outputs; a multi-mode interference coupler connecting the optical inputs to the optical outputs, the coupler including: a first multi-mode waveguide that has a first side surface, a second side surface, a first end, and a second end, the first side surface and the second side surface extending in a direction of a first axis, the first end and the second end extending in a direction intersecting with the first axis; a first waveguide group including a plurality of semiconductor regions connected to the first end of the first multi-mode waveguide, the plurality of semiconductor regions of the first waveguide group optically coupling the optical outputs to the first multi-mode waveguide; a second waveguide group including a plurality of semiconductor regions connected to the second end of the first multi-mode waveguide, the plurality of semiconductor regions of the second waveguide group optically coupling the optical inputs to the second end of the first multi-mode waveguide a first semiconductor region that has a side surface extending substantially parallel to the first side surface of the first multi-mode waveguide; and a first external semiconductor region that is provided on an external side of the first waveguide group, the first external semiconductor region having a side surface extending substantially parallel to an edge of the first waveguide group, wherein adjacent semiconductor regions of the first waveguide group have distances therebetween, at least one of the distances having a maximum value, the side surface of the first semiconductor region is spaced apart from the first side surface of the first multi-mode waveguide by a distance smaller than or equal to a reference value equal to said maximum value of the distances, and the side surface of the first external semiconductor region is spaced apart from the edge of the first waveguide group by a distance smaller than or equal to the reference value.