Coupled spiral-shaped microring resonator-based unidirectional add–drop filters with gapless coupling

摘要

In this paper, a new type of coupled spiral-shaped microring resonator-based filter with a waveguide butt-coupled to a spiral notch, which can significantly relax the fabrication constraints, is reported on. Our two-dimensional finite-difference time-domain calculations suggest resonance splitting which is due to the strong inter-cavity coupling. The novel spiral ring-shaped filter is found to be operating as a band-pass filter with a many-element cascaded spiral-shaped microring resonator device. As the number of cascaded microring resonators increases, the lineshapes become inhomogeneously broadened and steeper. For the eight-element device, the broadened lineshape results in periodic rejection bands with ~ 6?nm bandwidth.