Fig. 1. Epitaxial wafer grown by MOCVD and PL test result. (a) Epitaxial wafer; (b) PL test result

Fig. 2. Light field distributions and normalized intensity distributions of light field under different modes. (a)‒(c) Light field distribution; (d)‒(f) normalized intensity distributions of light field

Fig. 3. Schematic of unstable cavity with high-order curved grating

Fig. 4. Curved grating mask pattern

Fig. 5. SEM images of curved grating. (a) Surface view; (b) side wall view

Fig. 6. COS packaged curved grating semiconductor laser

Fig. 7. P‒I‒V characteristics of different lasers

Fig. 8. Spectra of curved grating edge-emitting DFB semiconductor lasers under different injection currents. (a) 450 mA; (b) 500 mA; (c) 550 mA

Fig. 9. Spectra of different lasers. (a) FP laser; (b) linear grating DFB laser; (c) curved grating DFB laser