Fig. 1. Schematic diagram of the Er:YAG vector ring laser. LD, laser diode; L, lens; M1–M5, mirror; ISO, optical isolator; QP, q-plate. The incident angle at M5 drawn in the figure is much larger than that in the actual experiment for clear.

Fig. 2. Input-output dependences of CVBs with p = 1 and p = 3 in bidirectional operation.

Fig. 3. (a) Doughnut profiles of fundamental Gaussian beams and CVBs with p = 1 and p = 3; (b) intensity distributions after passing through a PBS; (c) observed intensity distributions after passing through a tilted lens.

Fig. 4. Input-output dependences of CVBs with p = 1 and p = 3 in unidirectional operation. Inset: input-output dependences of the fundamental Gaussian beam in unidirectional operation.

Fig. 5. Doughnut profiles of CVBs with p = 1 and p = 3 in unidirectional operation and the corresponding intensity distributions after passing through an analyzer with different axis angles.

Fig. 6. Scanning spectra of the output CVB (p = 3) in (a) bidirectional operation and (b) unidirectional operation.

Fig. 7. (a) Schematic diagram for measuring the relative OAM weight of generated beams; (b) the measured OAM weight distribution through the SPP embedded back-converted method.