Fig. 1. Gratings designed to generate 5×5 beams with different normalized intensities (I) and topological charges (l) with corresponding diffraction orders. (a) Schematic of a 5×5 continuous grating structure. (b) Simulated Gaussian beams. (c) The computed phase profile. (d) Far-field diffraction patterns when Gaussian beams propagate through (c): (−2,1)l = 2, (1,1)l = 3, (2,−2)l = 1, (2,2)I = 0.5, (1,−1)I = 0.5, (−1,−2)I = 0.4, (−1,0)I = 0.3, (−1,2) a missing order.

Fig. 2. Schematic of beam combination at any angles with a continuous grating. (a) Beam combination diagram. (b) Changing topological charges and combining beams at the same time.

Fig. 3. System of beam combination. LD—laser diode; L1—convex lens; PBS1, PBS2, PBS3—polarization beam splitter; SLM—liquid-crystal spatial light modulator; HWP—half-wave plate; QWP1, QWP2—quarter-wave plate; QP—q-plate; M—reflective mirror; AS—aperture stop, and CCD—CCD camera.

Fig. 4. Column (a) and column (b) are the Gaussian beams and OAM beams before the beam combination, respectively. Column (c) is the interference patterns after the beam combination.

Fig. 5. Experimental results when the grating constant is changed in proportion with the diffraction orders. The grating constants corresponding to (a), (b), (c), and (d) are, respectively, T=20λ, 80λ, 140λ, and 200λ.

Fig. 6. Columns (a) and (b) are the situations that change the position of the reflective mirror (incident angles). Column (c): combining beam and changing topological charge at the same time.