Very low insertion loss arrayed-waveguide grating with vertically tapered waveguides

We propose and demonstrate a very low insertion loss silica-based arrayed-w aveguide grating (AWG) achieved using a novel structure, which has vertical ly tapered waveguides between arrayed-waveguides to reduce the slab-to-arra yed-waveguide transition loss. A spot-size converter is also incorporated i n the AWG to reduce the fiber-to-waveguide coupling loss, The structure can he formed by a process involving the conventional photolithography and rea ctive ion etching. The structure provided a loss reduction of 1.5 dB, Moreo ver, we have successfully obtained a minimum insertion loss of 0.75 dB with a crosstalk of -40 dB and polarization-independent operation.