Optically reconfigurable polarized emission in Germanium.

Light polarization can conveniently encode information. Yet, the ability to tailor polarized optical fields is notably demanding but crucial to develop practical methods for data encryption and to gather fundamental insights into light-matter interactions. Here we demonstrate the dynamic manipulation of the chirality of light at telecom wavelengths. This unique possibility is enrooted in the multivalley nature of the conduction band of a conventional semiconductor, namely Ge. In particular, we demonstrate that optical pumping suffices to govern the kinetics of spin-polarized carriers and eventually the chirality of the radiative recombination. We found that the polarized component of the emission can be remarkably swept through orthogonal eigenstates without magnetic field control or phase shifter coupling. Our results provide insights into spin-dependent phenomena and offer guiding information for the future selection and design of spin-enhanced photonic functionalities of group IV semiconductors.