This is similar to the Jones matrix. As long as you can extract E scatterig for H and V compoments, you can excite the simulation with EH and EV. Suppose EH and EV have amplitude of 1 v/m, then the simulated scattering E will be the same as S, corresponding to H and V components.
BTW: Here is Photonics forum for Lumerical products. If you have questions for other products, please post questions to the proper forum: https://forum.ansys.com/
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