Abstract: The present invention relates to a semiconductor optical tap comprising: a multimode interferometer (MMI) (6); an input waveguide (1) coupled to the MMI; a first output waveguide (2) coupled to the MMI; and a second output waveguide (3) coupled to the MMI. The first and second output waveguides (2,3) overlap (d) such that unequal portions of light are coupled from the MMI into the first and second output waveguides (2,3). The input waveguide (1) and the first and second output waveguides (2,3) may have a rib structure. They may also be adiabatically tapered waveguides. The first and second output waveguides (2,3) may have different starting widths.

Abstract: In the present invention, profiling of the end facet of an optical waveguide reduces the amount of reflected light propagating in the waveguide. In a conventional waveguide, the effective reflectivity experienced by light at a facet is determined by the modal content of the light and the refractive index of the waveguide (core and cladding) and other material at either side of the dielectric interface, which constitutes the facet. In the present invention, depending upon the modal content of the light, the waveguide dimensions and the refractive indices at the dielectric interfaces, we adjust the profile of the facets so that it is no longer planar and so substantially reduce the amount of reflected light propagating back along the waveguide. This reduction in “effective reflectivity” can be due to an increase in the loss experienced by any reflected light or due to an increase in the amount of light transmitted.