A set of high performance single‐ and multiple‐stripe Alx′Ga1-x′As ‐AlxGa1-xAs quantum‐well heterostructure (QWH) laser diodes coupled to an external grating cavity is used to demonstrate the tuning properties of a semiconductor laser at short wavelength (λ≲7300 Å). A single‐stripe laser diode (6‐μm stripe width) with a single AlxGa1-xAs (x∼0.22) quantum well of size Lz≊400 Å is broadly tunable (7080≤λ≤7370 Å, Δℏω∼70 meV) and delivers a single dominant longitudinal mode of moderate output power (Pout∼50 mW at 200 mA, pulsed). In continuous (cw) operation (I=135 mA) a single‐stripe laser has a 36‐meV tuning range, 7168≤λ≤7322 Å. Phase‐locked twenty‐ and forty‐stripe diodes (3.5‐μm stripe width) from the same QWH wafer are capable of single‐longitudinal‐mode output at higher power (peak Pout∼1.6 W at a 8.0‐A, 200‐ns pulse) although at slightly longer wavelength and reduced tuning range (7225≤λ≤7425 Å). Data are presented illustrating the wavelength dependence of the gain and power output as well as the partial homogeneous broadening and phase‐locked nature of the QWH laser arrays. The difference in performance of the multiple‐stripe diodes compared with the single‐stripe structure can be attributed to the internal coupling of the optical field in neighboring stripes and the reduced threshold current density.