Fig. 1. High-refractive-index ring structure and simulation results^[14]. (a) Refractive index distribution; (b) mode energy distribution at different core refractive indices

Fig. 2. High-refractive-index ring structure and experimental results^[15]. (a) Refractive index distribution; (b) output spot energy distribution

Fig. 3. Microstructured fibers for beam shaping^[16]. (a) Fiber cross section; (b) three-dimensional energy distribution after shaping

Fig. 4. Energy distribution with different inner core sizes^[16]

Fig. 5. Cross section of microstructured fiber for obtaining the flat-top fundamental mode and the obtained flat-top fundamental mode^[17]. (a) With one air hole replaced by the fiber core; (b) with seven air holes replaced by the fiber core

Fig. 6. Flat top mode fiber^[18]. (a) Cross section; (b) refractive index profile; (c) a flat mode simulated in a fiber

Fig. 7. Simulation results at different wavelengths^[18]. (a) Flatness of the mode energy distribution at different wavelengths; (b) energy distribution profile of the fundamental mode at different wavelengths

Fig. 8. Experimentally obtained fundamental mode energy distribution profiles at different wavelengths^[18]. (a) From 650 nm to 1650 nm; (b) from 950 nm to 1150 nm

Fig. 9. Cross section of Ytterbium-doped leakage channel fiber^[19]

Fig. 10. Experimental and simulation results^[19]. (a) Nearly flat-top fundamental mode; (b) fundamental mode intensity distribution with different refractive index differences

Fig. 11. Schematic diagram of the experiment of the misaligned alignment of the incident laser in the radial and axial directions^[22]

Fig. 12. Beam intensity profile at the near field. (a) Misaligned in radial (x-direction) only^[22]; (b) misaligned in axial (z-direction) and radial (x-direction) ^[22]

Fig. 13. Experimental setup^[23]

Fig. 14. Output spot of the single-mode laser after passing through multi-mode fibers with different core diameters^[23]. (a) Core diameter of 600 μm; (b) core diameter of 400 μm; (c) core diameter of 200 μm

Fig. 15. Output spot of the single-mode laser after passing through the multi-mode fiber of different lengths^[23]. (a) 10 cm; (b) 30 cm; (c) 2 m

Fig. 16. Experimental setup^[24]. (a) Beam shaping device with all-fiber structure; (b) special multimode fiber

Fig. 17. Ordinary multimode fiber and special multimode fiber^[24]. (a) Number of modes; (b) shaping effect

Fig. 18. Long period gratings for beam shaping^[27]. (a) Schematic diagram of experiment; (b) transmission spectrum of the LPG

Fig. 19. Experimental results^[27]. (a) 2.1% fundamental mode is optically coupled into LP₀₃ mode; (b) no fundamental mode is optically coupled into LP₀₃ mode

Fig. 20. Experimental results^[27].(a) Spot energy distribution at different observation distances; (b) spot energy distribution at different wavelengths at a distance of 12 mm

Fig. 21. Long period grating for 1 μm laser shaping and experimental results^[28]. (a) Transmission spectrum of the long period grating; (b) energy distribution of the spot at 13 mm from the fiber end face

Fig. 22. Schematic diagram of tapered fiber beam shaping^[32]

Fig. 23. Spot energy distributions observed at L_b=12 mm^[32]. (a) 1570.1 nm; (b) 1589 nm

Fig. 24. Spot energy distribution at different positions (L_b=7 mm and 12 mm) after passing through the tapered fiber and after passing through the single-mode fiber^[32]. (a) 1570.1 nm; (b) 1589 nm

Fig. 25. Tapered fiber structure for beam shaping^[33]. (a) Beam shaping device with all-fiber structure; (b) variation of mode content with propagation distance; (c) experimental results

Fig. 26. Experimental setup^[34]. (a) Only the core is etched; (b) core and cladding are etched

Fig. 27. Spot energy distribution^[34]. (a) Unetched single-mode fiber; (b) single-mode fiber after 3 min of etching; (c) single-mode fiber after 4 min of etching

Fig. 28. Spot energy distribution observed when fiber tip is at different distances from the CCD camera^[34]. (a) 0.5 mm; (b) 2 mm; (c) 2.1 mm; (d) 2.5 mm

Fig. 29. Square core fiber for beam shaping^[36]. (a) Fiber cross section; (b) three-dimensional energy distribution of output spot

Fig. 30. Fiber cross section^[37]. (a) Fiber end face; (b) cladding air hole

Fig. 31. Near field spot intensity distributions^[37]. (a) 633 nm; (b) 1060 nm; (c) melting indium tin oxide with a 1060 nm shaping laser

Fig. 32. Cross section of rectangular core fiber^[38]

Fig. 33. Experimental results^[38] . (a) Spot images when incident with multimode beam; (b) spot images when incident with Gaussian beam

Fig. 34. Experimental setup and results^[39]. (a) Fiber cross section; (b) refractive index distribution; (c) spot energy distribution after 1 m of homogenized fiber

Fig. 35. Spot energy distributions of coupled fundamental mode and second-order mode with different ratios^[40]

Fig. 36. All-fiber structure beam shaping device^[41]

Fig. 37. Experimental results^[41]. (a) Two-dimensional energy distribution diagram of the "doughnut" light spot; (b) two-dimensional energy distribution diagram of the flat-top light spot; (c) three-dimensional energy distribution diagram of the flat-top light spot

Fig. 38. Experimental setup and result diagram of beam shaping for the incoherent superposition structure of fundamental mode and orbital angular momentum^[42]