Injection-locking of gain-guided diode laser arrays: influence of the master beam shape

According to a previously reported model [IEEE J. Quantum Electron. 27, 396 (1991)], the properties of injection-locked gain-guided diode laser arrays depend on the geometric characteristics of the master beam, such as the size of its waist and its incidence angle. Experimentally, two injection configurations are of particular interest: the focused injection, in which the master beam is focused on one stripe of the slave array, and the wide-beam injection, in which the master beam is shone on the whole or a part of the width of the array. We investigate experimentally and compare these two configurations. In particular, we show that, in agreement with our theory, changing the geometry of the master beam greatly alters the far-field patterns, the locking bandwidth, and the spectrum of the locked array. We also compare the injection angle sensitivity and the beam-steering properties of the two configurations. Observations confirm our predictions, and optimal configurations are proposed.