Abstract: A novel and efficient method for polarization conversion, particularly from linear polarization to circular polarization, and, importantly, vice versa, is obtained using shapeanisotropic self-assembled quantum dots, which, having the advantage of extremely small size (nanometer scale), may be readily incorporated into photonic crystals and/or other optical components. Such devices also have the advantage of working in the absence of an applied magnetic field. Such devices also, when a voltage bias is applied, can be used to manipulate electron spin by manipulating light polarization in the same circuit, and vice versa. This permits a high degree of control for either or both of these in spintronics and/or optical devices, the biased quantum dot being used as a nanometer scale electro-optic modulator. Components utilizing the method and/or devices may be used as part of highly compact optical computing networks and/or spintronics systems for e.g.