It is possible to obtain the frequency conversion in periodically poled crystals ) on the several types of quasi-phase-matching simultaneously.
     For SHG the exception is the following. If there is conditions of frequency conversion for two simultaneous types of interaction (for example, OOE and EEE), than the phase-mathing conditions for third type (OEE in example case) will take place automatically. Also this relation take place for EEO, EOO, EEO in uniaxial crystals, and SSF, FFF, SFF and FFS, SSS, FSF combinations in biaxial crystals.

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