Fig. 1. Simulation model for coupling structure of NV^- color center and diamond nanopillar

Fig. 2. Variation of each parameter with nanopillar size. (a) Variation of F_p with H_T and D at H_L= 270 nm; (b) Variation of β_t with H_T and D at H_L= 270 nm; (c) Variation of η with H_T and D at H_L= 270 nm; (d) Variation of F_p with H_L and D at H_T= 130 nm;

Fig. 3. Variation of composite index Z with nanopillar size. (a) Variation of Z with H_T and D at H_L= 270 nm;(b) Variation of Z with H_L and D at H_T= 130 nm

Fig. 4. (a) Influence of structural dimensional error on Z; (b) Photon emission angle distribution; (c) Electric field distribution in the cross-section of nanopillar perpendicular to the polarization direction of the color-center ; (d) Electric field distribution in the cross-section of nanopillar parallel to the polarization direction of the color-center