Channel-add operation of a device using defects in a two-dimensional photonic crystal slab

A channel add-filtering function of a device based on defects in a two dimensional photonic crystal slab is investigated in addition to a channel drop-filtering function reported previously. It is considered that photons irradiated to a point defect from free space are trapped by the point defect, are transferred to a line defect waveguide nearby, and are emitted from the waveguide edge. It is shown that the spectrum of the add-filtering function is almost same as that of the drop-filtering function, which demonstrates that photons can be not only dropped-from but also added-to a line-defect waveguide through the resonant trapping by point defects.