The flow-induced structure and dynamics of concentration fluctuations in near-critical polymer solution have been investigated using the technique of polarimetry. Specifically, this article presents scattering dichroism of a single-phased, semidilute solution of polystyrene in dioctyl phthalate (PS/DOP) subjected to small amplitude oscillatory shear flow. The measured frequency response is compared to results obtained using the Onuki-Doi theory, which relates dichroism to structure factor, and the Helfand-Fredrickson model, from which the structure factor is calculated. The predictions are in good qualitative agreement with the experimental data when stress relaxation is taken into account in the constitutive equation relating stress to strain in the system. Our results demonstrate that the strength of the coupling between viscoelastic stress and flow governs the behavior of concentration fluctuations in semidilute polymer solutions under oscillatory shear flow.