Three-dimensional quantum photonic elements based on single nitrogen vacancy-centres in laser-written microstructures

To fully integrate quantum optical technology, active quantum systems must be combined with resonant microstructures and optical interconnects harvesting and routing photons in three diemsnsions (3D) on one chip. We fabricate such combined structures for the first time by using two-photon laser lithography and a photoresist containing nanodiamonds including nitrogen vacancy-centers. As an example for possible functionality, single-photon generation, collection, and transport is successfully accomplished. The single photons are efficiently collected via resonators and routed in 3D through waveguides, all on one optical chip. Our one-step fabrication scheme is easy to implement, scalable and flexible. Thus, other complex assemblies of 3D quantum optical structures are feasible as well.