Coherence collapse and low-frequency fluctuations in quantum-dash based lasers emitting at 1.57 μm

Optical feedback tolerance is experimentally investigated on a 600-μm-long quantum-dash based Fabry-Pérot laser emitting at 1.57μm. While quantum-dashes are structurally intermediate to quantum-wells and quantum-dots, the observed behaviour is distinctly like that of a quantumwell based laser but with greater stability. Coherence collapse and lowfrequency fluctuation regimes are observed and are reported here. The onset of the coherence collapse regime is experimentally determined and is found to vary from -29 dB to -21 dB external feedback level when increasing the current from twice to nine times the threshold current.