Fig. 1. Multiple physical dimensions of photons and twisted light carrying OAM.

Fig. 2. Classification of complex optical fields and their applications on different platforms.

Fig. 3. Illustration of data information transfer using complex optical field modulation, multiplexing and multicasting.

Fig. 4. SEM images of a fabricated silicon microring. (a) Waveguide cross section; (b) grating coupler; (c) microring; (d) coupling region between the bus waveguide and bending waveguide.

Fig. 5. Measured results of chip-scale data information transfer in a silicon microring using complex amplitude modulation. (a) Spectra of eight wavelength channels (W1-W8); (b) Bit-error rate (BER) versus received optical signal-to-noise ratio (OSNR) for all eight-channel OFDM/OQAM 256-QAM data transmissions; (c)-(e) constellations of 256-QAM signals. B-to-B, back-to-back; FEC, forward error correction.

Fig. 6. Concept and principle of high-speed adaptive Bessel beam modulation through turbulence. BPG, bit-pattern generator; IM, intensity modulator; BS, beam splitter.

Fig. 7. Measured results of 20 Gbit/s Bessel beam modulation link for free-space data information transfer. (a) BER performance; (b)-(d) eye diagrams; (b) B-to-B; (c) before and (d) after turbulence compensation; (e) temporal waveforms.

Fig. 8. (a) Concept, (b) principle, and (c) results of spatial mode modulation for data information transfer in fiber.

Fig. 9. SEM images of fabricated silicon mode (de)multiplexer. (a) Two-mode; (b) three-mode; (c) asymmetrical directional coupler; (d) grating coupler.

Fig. 10. Measured BER performance and constellations of (a) two-mode and (b) three-mode (de)multiplexing using OFDM 256-QAM signals. I1-I3, input ports; O1-O3, output ports.

Fig. 11. Concept of full-duplex data information transfer using OAM multiplexing in an OAM fiber.

Fig. 12. Measured BER performance and constellations of full-duplex 20 Gbit/s QPSK data information transfer using OAM multiplexing in a 1.1 km OAM fiber. EFEC, enhanced FEC.

Fig. 13. (a) Relative refractive index profile and (b) photo of OAM fiber. (c1)-(c10) Measured OAM and demodulated Gaussian-like intensity profiles after 50 km fiber transmission.

Fig. 14. Measured BER performance of OAM multiplexing data information transfer in the 50 km OAM fiber.

Fig. 15. On-chip N-fold OAM multicasting using V-shaped antenna array (metasurface).