When making a design of the cubic phase plate testing system using computer generated hologram as the null lens

two very important questions are emerging. They are the wavefront aberration of cubic phase in propagation and the separation of the diffraction orders. The opinion is presented in this paper that the cubic phase introduces higher order aberration as it propagates. And the expression of the aberration for the cubic phase when propagating is given in detail. From the formula we can see that the high order aberration increase as the propagation distance l increase. The theoretic foundation for the diffraction orders separation of the testing wavefront diffracted by the CGH. To prove the theories

we take a design of the cubic phase plate testing system for example. The results coincide with the theoretical formula we got.