Microscopic model of quantum noise in semiconductor lasers

Summary form only given. The intensity noise properties of single-mode semiconductor lasers at zero-frequency are studied on the basis of an operator set of equations for the field, the material polarization, the microscopic carrier distribution and the total carrier number in each band. The theory includes the noise effects of (i) Coulomb scattering processes, which tend to drive the carriers into intraband Fermi-Dirac quasi-equilibrium, (ii) spectral hole burning, i.e. the carrier deviation from quasi-equilibrium induced mainly by light-matter interaction, (iii) pump-blocking, which, in conformity with the Pauli exclusion principle, prevents the pumped carriers whose k-state is already occupied from entering the active layer. All these phenomena are not considered in the standard theory, which starts from a macroscopic set of equations for the field and the total carrier population only. Our analysis shows that Coulomb scattering and spectral hole burning have only negligible effects on the noise properties of the laser, while pump-blocking can bring a sizable increase of intensity noise. Under certain parametric conditions this increase can raise the noise level above the shot noise limit, thus destroying any squeezing. We show that the pump-blocking induced additional noise originates from the field and the material polarization. Since the suppression of field and polarization noise is ensured respectively by destructive interference of field fluctuations at the output mirror and by gain saturation, we conclude that pump-blocking hampers both these phenomena.