Reflectance Reduction in a Whiskered SOI Star Coupler

In this letter, we evaluate how the background noise is modified within a whiskered-shaped star coupler, optimized to reduce the reflectivity of its internal surfaces to reduce the back-scattered light. This letter is carried out by analyzing the Fabry-Perot interference due to the reflections between the input focal plane of the star coupler and the output facet of the waveguides. By comparing a whiskered star coupler with a standard one, we find a reduction in the star coupler reflectance of more than one order of magnitude. The experimental results are supported by a theoretical model and by numerical simulations.