  The effect of irregular hole shape on the spectrum and radiation losses of a
photonic crystal waveguide is studied using Bloch-mode expansion. Deviations
from a perfectly circular hole are characterized by a radius fluctuation
amplitude and correlation angle. It is found that the parameter which
determines the magnitude of the effect of disorder is the standard deviation of
the hole areas. Hence, for a fixed amplitude of the radius fluctuation around
the hole, those effects are strongly dependent on the correlation angle of the
irregular shape. This result suggests routes to potentially improve the quality
of photonic crystal structures.
