GaSb based broad-area (BA) diode lasers with watt-class emission power and improved divergence were demonstrated using a fishbone shape microstructure. The influences of etching depth of microstructure on the emission and far-field performance were investigated. It was found that the utilization of microstructure was able to enhance the emission power evidently. Moreover, the deeply etched microstructure was more effective on the decrease of mode number and lateral far-field divergence. Compared with the device without microstructure, the deeply etched BA lasers show 57% decrease in the lateral far-field angle defined by the 95% power content, and the maximum continuous-wave (CW) output power exceeds 1.1 W.