  What we believe to be a new type of resonant coupling of an incident bulk
wave into guided modes of a slab with a thick holographic grating is shown to
occur in the presence of strong frequency detunings of the Bragg condition.
This happens through the reflection of the strongly noneigen +1 diffracted
order with the slab-grating boundaries, the resultant reflected waves forming a
guided slab mode. Rigorous coupled-wave analysis is used for the numerical
analysis of the predicted resonant effects. Possible applications include
enhanced options for the design of multiplexing and demultiplexing systems,
optical signal-processing devices, optical sensors, and measurement techniques.
