Disorder-Induced Losses in Photonic Crystal Slabs

Recent results of a theoretical treatment of disorder-induced losses in photonic crystal (PhC) slabs are presented. The formalism is based on a guided-mode expansion method with a perturbative treatment of coupling to leaky PhC modes. Propagation losses are calculated for line-defect waveguides in PhC slabs defined in a high-index membrane, in particular for W1 and W1.5 waveguides in the triangular lattice, within a size-disorder model. The effects of backscattering into the counter-propagating mode are treated. Local modifications of the electromagnetic field induced by disorder (i.e., disorder-induced local-field effects) are evaluated and are found to be small for the considered systems. The results confirm that the W1.5 waveguide with increased channel width has strongly reduced losses as compared to the standard W1 waveguide geometry