Photonic-crystal heterostructure waveguides

Abstract

Photonic crystals (PC) are periodic dielectric structures that, if suitably designed, prohibit light propagation within a frequency band even though the constituent materials may be transparent in this range. One of the remarkable applications of such artificial photonic materials has been to provide guiding of light. Ultimately, to guide light in directions other than straight lines, PC waveguide (PCW) bends are needed, and thus are expected to be essential building blocks of photonic integrated circuits. While bending light through large angles is possible with conventional waveguides, the corner radii of such bends cannot typically be reduced to the electromagnetic wavelength, which hinders the realization of extremely compact devices. And though sharp two-dimensional (2-D) PCW bends have been proposed, the transmission is typically low and/or narrow band. Here we focus on PCWs obtained by introducing line defects in otherwise period 2-D PCs with the aims of enhancing the typical poor and low-bandwidth transmission through tight bends. We show how PCW bends occurring at heterojunctions between different PCs may enable unprecedented flexibility in meeting these aims. The deformation introduced to the usual PC lattice lifted off the angle constraint and resulted in the power transmission greater than 90% over in the 95-nm bandwidth.