Power exchange in grating-assisted couplers

The power exchange between two grating-coupled waveguides is studied and found to depend on the beat length between the two modes and the spacing of the coupled waveguides. It is an oscillatory function of coupling length with an extremum at those values of coupling length that are an integer multiple of the beat length. Complete power transfer can be achieved only if the two waveguides are far from synchronism and weakly coupled.<
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