Loss reduction of photonic crystal waveguide fabricated by the autocloning technology

The heterostructured photonic crystal waveguide fabricated by the autocloning technology allows fabrication jointly with other functional devices. Hence, this approach is useful for elemental components for the next-generation high-function planar optical circuits. When this waveguide is used for interconnection of optical circuits, its propagation loss should be as small as possible. In this investigation, Ta₂O₅/SiO₂ is selected as the construction material. Further, by using a waveguide configuration minimizing the scattering loss, substantial loss reduction was achieved. It is especially effective to use a simple flat multilayered film structure. A loss reduction up to a propagation loss of 0.1 dB/mm was realized. The present waveguide has a small coupling loss of 0.43 dB with an existing optical fiber (a high-Δ fiber with a mode field diameter of 2.7 μm) and hence is easily adapted to the optical communication system. The heterostructured photonic crystal waveguide is thus extremely practical.