Fig. 1. Net gain coefficients at Bragg wavelength of semiconductor lasers

Fig. 2. Far field distributions after single-chip collimation. (a) Spot energy distribution; (b) spot size in fast axis direction; (c) divergence angle in fast axis direction

Fig. 3. Schematic of spectral experimental setup of semiconductor laser with VBG external cavity

Fig. 4. Output spectra of semiconductor laser with VBG external cavity. (a) Spectra under different pumping currents; (b) spectra under different operating temperatures

Fig. 5. Spectral stability under free running and grating locking. (a) Peak wavelengths at different pumping currents; (b) peak wavelengths at different operating temperatures

Fig. 6. Output spectra of semiconductor lasers with VBG external cavities under different end face reflectivity values. (a) 0.40%; (b) 0.20%; (c) 0.02%

Fig. 7. External cavity mode ratio of semiconductor laser with VBG external cavity

Fig. 8. Power output characteristics of semiconductor laser with VBG external cavity.(a) P-I curves; (b) external cavity efficiency curves