Trapping and emission of photons by a single defect in a photonic bandgap structure

By introducing artificial defects and/or light-emitters into photonic bandgap structures1,2, it should be possible to manipulate photons. For example, it has been predicted2 that strong localization (or trapping) of photons should occur in structures with single defects, and that the propagation3,4 of photons should be controllable using arrays of defects. But there has been little experimental progress in this regard, with the exception of a laser5 based on a single-defect photonic crystal. Here we demonstrate photon trapping by a single defect that has been created artificially inside a two-dimensional photonic bandgap structure. Photons propagating through a linear waveguide are trapped by the defect, which then emits them to free space. We envisage that this phenomenon may be used in ultra-small optical devices whose function is to selectively drop (or add) photons with various energies from (or to) optical communication traffic. More generally, our work should facilitate the development of all-optical circuits incorporating photonic bandgap waveguides and resonators.