Fig. 1. Schematic diagram of the PVB generation and the corresponding characterization sections. LD, laser diode; HR-FBG, high-reflectivity fiber Bragg grating; YDF, ytterbium-doped fiber; CPS, cladding power stripper; SMF, single-mode fiber; ISO, isolator; DMD, digital micromirror device; BS, beam splitter; CCD, charge-coupled device.

Fig. 2. Generation of a PVB using super-pixel wavefront shaping. The target intensity (a) and phase (b) profiles of the PVBs. (c) Binary DMD patterns. Theoretical intensity (d) and phase (e) profiles of the output using super-pixel wavefront shaping. (f) Experimentally measured intensity profiles.

Fig. 3. Flat-top PVB generation. The target intensity (a) and phase (b) profiles of the flat-top PVBs. (c) Binary DMD patterns. Theoretical intensity (d) and phase (e) profiles of the flat-top PVBs. (f) Experimentally measured intensity profiles.

Fig. 4. Block diagram of the GAFA-based wavefront shaping for flat-top PVB generation. TP, target phase; TI, target intensity; MI, measured intensity.

Fig. 5. Evolution of the measured intensity profiles under GAFA-based feedback modulation. (a) The unmodulated intensity profiles. (b)–(e) The real-time intensity profiles for iteration numbers 2, 5, 40 and 50, respectively.

Fig. 6. Characteristics of flat-top PVB generation. Evolution of the speckle contrast and the mean intensity value for topological charges of 1 and 20 (a1), 50 and 100 (a2). Evolution of the curve in the central cross-section for the topological charges of 1 (b1), 20 (b2), 50 (b3) and 100 (b4). Interference patterns of the modulated flat-top PVB for the topological charges of 1 (c1), 20 (c2), 50 (c3) and 100 (c4).