Collecting single photons from a cavity-coupled quantum dot using an adiabatic tapered fiber

We demonstrate efficient in-plane optical fiber collection of single-photon emission from a quantum dot embedded in a photonic-crystal cavity. This was achieved via adiabatic coupling between a tapered optical fiber and a tapered on-chip photonic waveguide coupled to a modified high-Q L3 photonic cavity, with a theoretical in-plane fiber-collection efficiency of 47%. Experimentally, this efficiency is measured by comparing the luminescence intensities collected by the fiber and by a NA 0.65 microscope objective placed above the cavity and reaches half of the theoretically expected value. Simulations show that the in-plane collection efficiency can be further increased to 77% by improving the dot-cavity coupling and by increasing the overlap length between the tapered fiber and waveguide. Near-unity adiabatic coupling is predicted for an overlap length of 5μm. The single-photon source was characterized by second-order correlation measurements giving g(2)(0)=0.17 under nonresonant excitation.