I may be wrong but here goes ......
Thinking about it briefly (very briefly), this will give you the ability to encode successive bits of data with different polarisation, the discrete sequence of the polarisation direction (in 3D) which is known to the creator but not to any unauthorised person who tries to read it. However, there will be a finite and limited set of possible polarisations otherwise an authorised recipient would not have the equipment to read it. It's like being presented with a box containing a bit of data then being told that there are in fact, say, 100 sub-boxes (determined by the polarisation direction) so which sub-box do you want?
Isn't this actually high density steganography? Or am I splitting hairs?