Backscattering and disorder limits in slow light photonic crystal waveguides

It is known that slow light propagation in disordered photonic crystal channel waveguides leads to backscattering and localization phenomena. The knowledge of the reflection of a slow light mode at a single disorder defect of the periodical structure can help to estimate the backscattering intensity and the localization length. Here, this Bloch-mode reflection is calculated in a simplified slow light waveguide using an eigenmode-expansion approach. We show that by properly engineering the waveguide, backscattering can be significantly reduced while maintaining the same low group velocity. A strong effect of the mode's anticrossing taking place in photonic crystal line-defects is demonstrated on backscattering. The localization length of slow light waveguides is estimated, which provides fundamental limits for the applicability of slow light waveguides.