Role of Bloch mode reshaping and disorder correlation length on scattering losses in slow-light photonic crystal waveguides

Abstract

Intrinsic disorder in photonic crystal waveguides occurs via rapid fluctuations of the air-dielectric interface and is typically characterized by a quadratic mean surface roughness and a surface correlation length. We theoretically study the impact of correlation length on extrinsic scattering losses and discuss the numerical implementation for several different waveguide designs. The role of correlation length is found to be strongly influenced by the underlying Bloch modes which are dependent on waveguide design and frequency, and can thus be partly controlled via spatial-dispersion engineering. For most frequencies and waveguide designs, we find an asymptotical increase in losses as the correlation length increases; however, we show that for some frequencies and designs, a maximum scattering loss is achieved for a finite correlation length. Our results also demonstrate the importance of choosing an appropriate correlation function for modeling quickly varying disorder.