An apparatus including a waveguide input coupler, a tapered branch waveguide, and a waveguide adaptor physically connected to the waveguide input coupler proximal end and to the branch waveguide proximal end. The waveguide input coupler includes a distal end having a distal end width and a proximal end having a proximal end width. The tapered branch waveguide includes a distal end having a distal end width and a proximal end having a proximal end width, the branch waveguide distal end width being greater than the branch waveguide proximal end width. The waveguide input coupler, the branch waveguide, and the waveguide adapter are configured to convert input light having a base transverse waveguide mode to output light having a higher-order waveguide mode.