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 $5\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\mathrm{m}$. The single-photon source was characterized by second-order correlation measurements giving ${g}^{(2)}(0)=0.17$ under nonresonant excitation.