Fig. 1. Schematic representation of the RDE of a CVB in scattered fields. The RDE spectrum is related to the OAM spectrum of the probe beam and the spiral spectrum of rotating object through a simple equation.

Fig. 2. Schematic of experimental layout for the RDE based on a CVB. P, polarizer. L1, L2, L3, L4, and L5, lenses. AP, aperture. M, mirror. BS, beam splitter. PD, photoelectric detector. (a) The spiral spectrum of rotating image O1 to be loaded on the DMD. (b) The DMD for emulating the targets.

Fig. 3. OAM amplitude spectra (left column), simulated (middle column) and experimental (right column) RDE frequency spectra of different CVBs. The rotating object is O1. The rotational speed Ω=27.78  Hz. The intensity profiles of corresponding probe beams are also shown as insets.

Fig. 4. RDE frequency spectra of CVBs with different OAM phase spectra and identical OAM amplitude spectrum. (a) OAM amplitude spectrum of the beams. (b1)–(d1) Different OAM phase spectra; (b2)–(d2) simulated and (b3)–(d3) experimental intensity profiles and RDE frequency spectra of different CVBs.

Fig. 5. Radial effect of RDE. (a) OAM amplitude spectrum of the CVB composed of two vortex beams with different beam radii. (b) Simulated results of RDE frequency spectrum. (c) Experimental results of RDE frequency spectrum.

Fig. 6. Tailoring OAM spectrum to compensate for the effect of misalignment. (a1)–(a4) OAM spectrum of the composite LG beam (l=±5), simulated and experimental RDE spectrum. (b1)–(b4) OAM spectrum of the composite LG beam (l=±5) with misalignment d=0.05w, simulated and experimental RDE spectrum. (c1)–(c4) OAM spectrum of the tailored CVB, simulated and experimental RDE spectrum with misalignment d=0.05w. The intensity and phase of (d), (e) composite LG beams (l=±5) and (f), (g) tailored CVB are also depicted. The red dotted line represents the center line of the spot.

Fig. 7. Comparison between multimode reception and single-mode reception schemes in a special case. (a) OAM spectrum of the probe beam. (b) Spiral spectrum of the rotating object. (c) RDE frequency of multimode reception. (d) RDE frequency of single-mode reception.

Fig. 8. The OAM amplitude spectrum, and the simulated and experimental RDE frequency spectrum of CVB with l=±17,±23. The rotating object is a metal disc. The rotational speed is Ω=65  Hz.

Fig. 9. Tailoring the OAM spectrum to compensate for the effect of large misalignment. (a1)–(a3) OAM amplitude and phase spectrum of the composite LG beam (l=±5) with misalignment d=1w, and simulated RDE spectrum. (b1)–(b3) OAM amplitude and phase spectrum of the tailored CVB, and simulated RDE spectrum with misalignment d=1w.