Stability of the single-mode output of a laser diode array with phase conjugate feedback

The stability of the output of a single-mode laser diode array with frequen cy selective phase conjugate feedback has been investigated experimentally. Both the long-term stability of the laser output and the sensitivity to fe edback generated by external reflection of the output beam are examined. Th e output power and the center wavelength are found to be extremely stable i n a 100 h stability measurement. External feedback of the output beam into the laser is seen to decrease both the spatial and the temporal coherence o f the output significantly. We outline an approach to obtain a stable singl e-mode output when external feedback is present using spatial filtering in the path of the output beam. (C) 2000 American Institute of Physics. [S0003 -6951(00)04505-8].