Optimizing the coupling efficiency of spontaneous parametric down-conversion photon pairs into single-mode fibers

Photon Pair Source based on PPLN‐Waveguides for Entangled Two‐Photon Absorption

“…We also estimate a single mode fiber coupling efficiency of 𝜂 coup ≈ 90%. [20,21] The insertion loss for the used single mode fused fiber optic coupler is given by 3.7 db which results in a transmission efficiency through the coupler of 𝜂 inser ≈ 43%. All these losses finally result in total detection efficiencies of…”

“…We also estimate a single mode fiber coupling efficiency of $${\eta}_{\text{coup}}\approx 90\%$$. [ 20,21 ] The insertion loss for the used single mode fused fiber optic coupler is given by $$3.7\;\text{db}$$ which results in a transmission efficiency through the coupler of $${\eta}_{\text{inser}}\approx 43\%$$. All these losses finally result in total detection efficiencies of $$$$\begin{align} {\eta}_{\mathrm{Singles}}& ={\eta}_{\mathrm{coup}}\cdot {\eta}_{\mathrm{inser}}\cdot {\eta}_{det}\approx 23\% \end{align}$$$$ $$$$\begin{equation} \def\eqcellsep{&}\begin{array}{cc} {\eta}_{\mathrm{Coin}}& ={\eta}_{\mathrm{coup}}\cdot {\eta}_{\mathrm{inser}}^{2}\cdot {\eta}_{det}^{2}\approx 6\% \end{array} \end{equation}$$$$for single and coincidence count rates.…”