Optical studies of a bright exciton provide only limited information about
the hole anisotropy in a quantum dot. In this work we present a universal
method to study heavy hole anisotropy using a dark exciton in a moderate
in-plane magnetic field. By analysis of the linear polarization of the dark
exciton photoluminescence we identify both isotropic and anisotropic
contributions to the hole g-factor. We employ this method for a number of
individual self-assembled CdTe/ZnTe quantum dots, demonstrating a variety of
behaviors of in-plane hole g-factor: from almost fully anisotropic to almost
isotropic. We conclude that, in general, both contributions play an important
role and neither contribution can be neglected.Comment: 7 pages, 4 figure