Reduction of excess intensity noise induced by external reflection in a gain-coupled distributed feedback semiconductor laser

The intensity noise of a gain coupling (GC) distributed feedback (DFB) laser under the influence of external optical feedback was measured. As a whole, the GC DFB laser was found less sensitive to reflection in terms of relative intensity noise (RIN). Principal results obtained from experiments are described. Intensity noise characteristics of the isolated GC DFB laser (in the absence of external reflection) are the same as those of the conventional IC DFB laser. RIN lower than 10 ^-14 Hz^-1 is attainable at an output power above 3 mW. Intensity noise induced by optical feedback from a remote object (600 mm) is 10-20 dB less in the GC DFB laser when the amount of the feedback is between 0.1 and 1%. Adjacent reflection (90 mm) causes virtually no increase in intensity noise of the GC DFB laser if the feedback is not large