Wave phenomena in a planar periodically corrugated waveguide are investigated in detail. It is shown that the corrugation causes resonant interaction between the transverse modes (standing waves). The interaction results in the non-Bragg nature resonances, which divide the spectrum of the mode into the subminizones and give rise to non-Bragg reflections. The width of the non-Bragg gap as well as the Bragg gap depends on the relative position of two periodic plates. It varies from zero to a maximum value upon shifting of one periodic plate with respect to another on the half period of the corrugation. When a frequency of the electromagnetic wave coincides with one of the gaps, only unidirectional propagation along grooves is allowed in the waveguide. Thus the shift of the plates switches the two-dimensional guiding structure to the unidirectional guide and creates the photonic stripe phase in such a periodic waveguide. (C) 2003 Elsevier B.V. All rights reserved.