Simultaneous generation of fundamental transverse-electric and transverse-magnetic modes in diamond micro-ring resonators doped with nitrogen-vacancy centers

Entangled photon pairs with orthogonal polarizations, namely the fundamental transverse-electric (TE) and the transverse-magnetic (TM), have important applications in quantum communication and quantum information processing. We report on the simultaneous generation of photons in TE and TM modes from diamond micro-ring resonators (radius: 2.25 µm) doped with nitrogen-vacancy centers and fabricated using Faraday-cage angled etching. Double peaks are observed in the photoluminescence spectra of the ring resonators. These double peaks are investigated in detail and are attributed to the simultaneous excitation of the fundamental TE and TM modes. Polarization-resolved measurements are performed to verify this interpretation.