[Laser] Polarization modulation (Was: High-power polarized light?)

[Tom Becker]

Polarization need not be binary; it can be any angle, can it not?

Instead of considering a polarized beam as two fixed-angle differential 
channels, might there be an advantage of phase modulation, using 
polarization as the medium?  How to convert phase to polarity is an 
interesting question but, once answered, why not use the entire rotation 
cycle rather than just two arbitrary positions in it?

Tom