Embodiments relate to a branching waveguide circuit where two or more waveguides branch from a main waveguide defining between them an intermediate region ranging from said main waveguide. The intermediate region comprises a plurality of holes of cladding material extending from the top of the core layer into intermediate material, said holes being arranged so that the depth of said holes increases away from said main waveguide with an average slope of the hole depth versus distance to main waveguide. This way, loss due to transition between the main and branching waveguides may be reduced.