Fig. 7.

Proof-of-principle demonstration of spin-orbit jointly controlled unidirectional coupling of waveguide modes. a Schematic of platform for receiving CVVs via spin-orbit unidirectional coupling effect. For devices of unity transverse-spin states in the evanescent region (σ_res = ±1), the propagation direction of coupled light in the waveguide, or the ratio of received power at the two ports P₁/P₂, is first subject to the sign of incident SAM state, sgn(σ_in). Meanwhile, at a given wavelength (λ_res), the incident spin-orbit states 〈σ_in, l_in〉 must obey the phase-matching condition l_in + σ_in = l_res for high-efficiency coupling. b–d Received power at Port 1 (P₁, blue bars) and Port 2 (P₂, red bars) of device WG_4–10 when the SAM state of incident wave σ_in = +1, 0, and −1, respectively. For each σ_in, CVVs at 5 resonance wavelengths of WG_4–10 (1578.61, 1583.11, 1587.59, 1592.11, and 1596.66 nm) and 11 OAM states (l_in = −5, −4, …, and +5) are illuminated on the device. At these five wavelengths, the CVVs emitted from the device would carry the topological charges of l_res = ±4, ±2, 0, ∓2, ∓4, respectively, when injecting light into Port 1 (2), as marked in blue (red) on the l_res axis in b–d. All measured power has been calibrated with respect to the lensed fiber coupling loss (Supplementary Note 10), and all data are normalized to the highest value in each l_res group