Polarization squeezing in vertical-cavity surface-emitting lasers

We further elaborate the theory of quantum fluctuations in vertical-cavity surface-emitting lasers (VCSEL's), developed by [Hermier Phys. Rev. A 65, 053825 (2002)]. In particular, we introduce quantum Stokes parameters to describe the quantum self-correlations and cross correlations between two polarization components of the electromagnetic field generated by this type of laser. We calculate analytically the fluctuation spectra of these parameters and discuss experiments in which they can be measured. We demonstrate that in certain situations VCSEL's can exhibit polarization squeezing over some range of spectral frequencies. This polarization squeezing has its origin in sub-Poissonian pumping statistics of the active laser medium.