Single longitudinal mode operation of semiconductor laser arrays with étalon feedback

The multiple longitudinal mode output of high-power diode-laser arrays is converted into single mode with 97% efficiency by optical feedback from a thin (<200 μm thick) étalon external to the laser. The coupled cavities formed by addition of the étalon favor a single longitudinal mode. Single-mode operation is retained at 0.1 MHz pulsed rates. Both the near-field and the far-field patterns of the laser array remain nearly unchanged while the array operates in a single longitudinal mode.