25-GHz spacing, 8-ch compact arrowhead arrayed-waveguide grating using v-bend waveguides

The novel compact arrowhead arrayed-waveguide grating (AWG) using v-bend waveguides in each arrayed waveguide is proposed and fabricated. The v-bend structure is useful to reduce bending area of a silica waveguide with low A (0.3%) to high A (0.8%) design. It is composed of curved single mode waveguides and a slab waveguide with an integrated elliptic metal mirror. The mirror structure in the v-bend waveguide is fabricated by the reactive ion etching of the deep trench with smooth and vertical side wall, and by the deposition of silver metal with chemical reaction. The proposed AWG with arrowhead shape has a footprint of only 1/10 of the conventional one with the same performance. The small footprint leads to low cost and to high-resolution because the small circuit is less subject to the fluctuation of the effective index of the substrate. In this paper, the 8-ch, 25 GHz spacing arrowhead AWG composed of the same v-bend structures in each arrayed waveguide in order to obtain the uniform propagation loss of the v-bend is fabricated with the effective index of 0.75 % silica and its property is reported. Its size of the slab and arrayed waveguide region is 1.3 mm x 15.5 mm and only 1/10 of the conventional type.