Diamond grown by chemical vapor deposition (CVD) was investigated using a polarization modulated scanning near field optical microscope. The authors found that the luminescence has spatial inhomogeneities and it is partially polarized. Confined emission shows differences in polarization angle up to 90 degrees. The study reveals a peculiar confined dichroic behavior in CVD materials and suggests that local crystal aggregates play a role in it. (c) 2006 American Institute of Physics.