Electrically controlled topological defects in liquid crystals as tunable spin-orbit encoders for photons.

We demonstrate experimentally that topological defects of vertically aligned nematic liquid crystal films induced by electric fields can be used as highly efficient natural optical spin-orbit encoders that do not need machining techniques. Moreover, we show that both the operating wavelength and operation mode of such natural quantum optical interfaces can be tuned in real time using low-voltage electric fields.