Fig. 4. Characterization of single-photon single-mode SAM-OAM beams.

(A) Intensity distributions of the single-photon emission obtained with different DONR spiral trajectories measured after the reflection from the SLM encoded with different orders of spiral phases. First row present the phase distribution for the SLM holograms with the topological charges of −3, −2, −1, 0, and 1. Second, third, and fourth rows present the intensity distributions obtained with the diverging, concentric, and converging spiral arrangements, respectively. (B and C) Mode purity of the single-photon source simulated (B) and measured (C) with the diverging spiral trajectory. (D) Second-order correlation function g⁽²⁾ of single-photon emission measured before and after the ND-NV coupling with the metasurface using 100 μW of 532-nm continuous laser. (E) Fluorescence spectrum of the single-photon emission measured before and after the ND-NV coupling.