Low-loss transmission band in photonic crystal waveguides with sharp cutoff at a frequency below the bandgap

We present TE transmission measurements of photonic crystal waveguides with high hole radius to period ratio r/¿ = 0.388. This geometry introduces a unique low loss transmission band in addition to the traditional PhC guiding band and very sharp transmission edges for devices with a length of 50 µm or longer. Finite difference time domain and plane wave expansion simulations confirm the results and show that the sharpness of the cutoffs can be explained by the spectral shape of the guiding mode in the band diagram. © 2011 Elsevier B.V. All rights reserved