Integrated coherent combining of angled-grating broad-area lasers

In this paper, we investigated coherent beam combining of angled-grating broad-area lasers in a completely integrated approach. We obtained the simultaneous coherent beam combining and single transverse mode operation on a single chip through the integrated coupling regions and the transverse Bragg resonance （TBR） gratings, respectively. The proposed combining method can be easily extended to a zigzag-like laser array. We analyzed the scalability of the zigzag-like combining structure and compared it with other coherent combining methods. Two and six angled-grating broad-area lasers are fabricated and coherently combined by use of the proposed method. The high contrast interference fringes within an overall single lobe envelope in the measured far field prove that the emitters in the array are indeed coherently combined. By p-side-down bonding, we obtained over l W output power with over 90% combining efficiency in the two coherently combined lasers.