We show theoretically that the frequency shifts that result from phase-mismatched cascaded processes under conditions of strong group-velocity mismatch can be significantly enhanced by local control of the nonlinearity with propagation. This control is possible with continuous variation of the poling period of quasi-phase-matched structures and can allow one to avoid saturation of the frequency shift. We theoretically demonstrate its applicability to high-quality, efficient frequency shifting of infrared pulses.
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