Channel-drop filters (CDFs) with photonic crystal slabs-connected between silicon channel waveguides and fabricated on an SOI water-were designed and fabricated and these demonstrated wavelength division demultiplexing. Results simulated with the two-dimensional finite-difference time-domain and plane-wave methods demonstrated that considering the impedance profile, which is directly correlated with the reflective coefficient at the highly reflective interface, is essential in designing a highly drop-efficient CDF structure. The fabricated filters attained a drop efficiency above 95% at around a wavelength of 1.6 mu m and a dropping bandwidth of 1.5 nm. (c) 2005 Elsevier B.V. All rights reserved.