Fig. 1. Schematic diagram of basic waveguide structure.a, Double quantμm well single barrier structure; b, Double quantμm well three barriers structure; c, Double quantμm well three barriers, thickening N-side barrier

Fig. 2. (a) Effect of different waveguide structures on the limiting factor; (b) Effect of different waveguide structures on the threshold gain ratio

Fig. 3. Effect of different waveguide structures on slope efficiency

Fig. 4. (a) PIV curves of triple-active regions semiconductor lasers with waveguide of A1 (red), A2 (green), A3 (blue); (b) Far field divergence angles of triple-active regions semiconductor lasers with waveguides of A1 (red), A2 (green), A3 (blue) in the vertical direction

Fig. 5. (a) PIV curve of triple-active regions semiconductor laser with B waveguide structure; (b) Divergence angle of far field in vertical direction of triple-active regions semiconductor laser with B waveguide structure

Fig. 6. (a) PIV curves of semiconductor lasers in the triple-active regions (black）and quadruple-active regions (red) with C waveguide structure; (b) Far field divergence angles of semiconductor lasers in the triple -active regions (black) and quadruple-active regions (red) with C waveguide structure

Fig. 7. Variation trend of far-field divergence angle of semiconductor lasers with riple-active regions under different threshold gain ratios; measured (black), simulated (red)