Generation and physical properties of a new form of unpolarized light

We start from our recent analysis of unpolarized light [J. Lehner et al., Phys. Rev. A 53 (1996) 2727] in which we distinguished two forms of unpolarized light, dependent on whether the field is invariant with respect to phase retardation (type I) or not (type II). First we show that optical mixing leaves the type unchanged. Our main objective is to devise a feasible experimental scheme for the generation of a new form of unpolarized light. Specifically, we point out that amplitude-stabilized unpolarized light is readily obtained with the help of two independently operated lasers. However, this light is of type II only, and we show that after passing a phase retarder it is no longer unpolarized, according to our general criteria. Experimentally, this becomes obvious from the fact that intensity fluctuations in a linear-polarization mode vary with the polarization direction