Fig. 1. Schematic diagram of the structure and cross section of the PL

Fig. 2. Mode transmission characteristics of the MSPL. (a) Schematic of single-mode fiber cross section; (b)‒(e) LP_11a, LP_11b, LP₀₁, OAM₀₁ mode

Fig. 3. Mode transmission characteristics of the NMSPL. (a) Schematic of single-mode fiber cross section; (b) output mode (not unique)

Fig. 4. Mode control simulation of three-mode NMSPL implementation

Fig. 5. Schematic diagram of coherent diode laser beam combining system based on PL

Fig. 6. System loss versus input power

Fig. 7. CCD near-field spot images of actual observed modes. (a) CCD near-field spot image in open-loop condition; (b)‒(d) CCD near-field spot images of LP₀₁, LP_11a and LP_11b in closed-loop condition