Ultralow-loss 1 /spl times/ 8 splitter based on field matching Y junction

A novel approach to an ultralow-loss Y junction is introduced and designed. By adding a succession of low index regions with properly chosen parameters in the straight waveguide before the branching region, the field mismatch is improved with a power presplitting effect. In order to show that effect we fabricated, tested, and compared 1 /spl times/ 8 splitters formed by cascaded conventional Y branches and the proposed field matching Y branch.