An antireflection-coated broad-area laser diode with an emitter size of $400\mathrm{\mu m}\times 1\mathrm{\mu m}$ and a chip length of $1500\mathrm{\mu m}$ is operated in a simple external cavity. For wavelength stabilization and to narrow the bandwidth a diffraction grating in a Littrow configuration is used. At an injection current of $9\mathrm{A}$ up to $6.8\mathrm{W}$ of optical output power and a resulting slope efficiency of $0.8\mathrm{W/A}$ could be achieved. Further, the bandwidth could be narrowed to $100\mathrm{pm}$ (FWHM), and a tuning range of $40\mathrm{nm}$ around $976\mathrm{nm}$ was obtained.