Reflection noise in vertical cavity surface emitting lasers

We describe the effect of back reflections on the relaxation‐oscillation peaks of low threshold (<6 mA), high intrinsic bandwidth (31 GHz) vertical cavity surface emitting lasers. With the largest feedback possible with our experimental arrangement, x=−5.8 dB, the relaxation‐oscillation peak breaks up into a series of sharp resonances with the spacing corresponding to the round tip frequency of the external cavity. In contrast to edge emitting lasers, no effect of reflections is observed for feedback levels x<−12.9 dB. This relative immunity of vertical cavity lasers to reflection noise is expected to be of interest for their applications to fiber communications.