OBSERVED FACTORIZATION OF EXCESS QUANTUM-NOISE THAT IS DUE TO BOTH POLARIZATION AND SPATIAL MODE NONORTHOGONALITY

When the eigenmodes of a laser cavity are nonorthogonal, the quantum-l imited linewidth of the laser is larger by an excess-noise factor than the standard Schawlow-Townes expression. Mode nonorthogonality can ex ist in the spatial domain, as in unstable-cavity resonators, but also in the polarization domain when the two polarization eigenmodes are no northogonal. We show experimentally that these two contributions are i ndependent of each other, i.e., that the excess-noise factor factorize s as a product of the spatial and polarization excess-noise factors. ( C) 1998 Optical Society of America.