  Two strong simultaneous resonances of scattering--double-resonant extremely
asymmetrical scattering (DEAS)--are predicted in two parallel, oblique,
periodic Bragg arrays separated by a gap, when the scattered wave propagates
parallel to the arrays. One of these resonances is with respect to frequency
(which is common to all types of Bragg scattering), and another is with respect
to phase variation between the arrays. The diffractional divergence of the
scattered wave is shown to be the main physical reason for DEAS in the
considered structure. Although the arrays are separated, they are shown to
interact by means of the diffractional divergence of the scattered wave across
the gap from one array into the other. It is also shown that increasing
separation between the two arrays results in a broader and weaker resonance
with respect to phase shift. The analysis is based on a recently developed new
approach allowing for the diffractional divergence of the scattered wave inside
and outside the arrays. Physical interpretations of the predicted features of
DEAS in separated arrays are also presented. Applicability conditions for the
developed theory are derived.
