Fig. 1. Passive coherent combining optical path of ring cavity based on auxiliary cavity phase-locking

Fig. 2. Single-mode amplifier power

Fig. 3. Output powers of system in open-loop and closed-loop states

Fig. 4. Output spectra of system. (a) Output spectrum after seeds pass through amplifier 1 a and amplifier 2 b; (b) output spectrum of system when loop is closed

Fig. 5. Longitudinal mode characteristics measured by F-P scanning interferometer

Fig. 6. Laser linewidth measured using time-delayed self-heterodyne method