Investigation of InGaAsP/InP DFB and FP Laser Diodes Noise Characteristic

In the paper, there are presented comprehensive noise characteristics (electrical and optical noise and correlation between electrical and optical fluctuations) investigations that were performed with the aim to clear up the reasons of short lifetime of laser diode (LD) and to find out LD design and fabrication features that can increase laser diode quality. Groups of different quality InGaAsP laser diodes have been investigated. Investigation has shown that Fabry-Perot (FP) laser facet coating with antireflection layer suppresses the mode hopping effect (that is characteristic for FP laser operation): LD facet coating reduces resonator quality and leads to the more stable laser operation. It is shown that noise characteristic features that indicate laser diode quality and reliability problems are the most significant at LD operation below and in the vicinity of the threshold region. These noise features are related to additional generation-recombination processes and current leakage out of the active region: some of the investigated laser structures have defects that lead to the leakage current, generation-recombination noise, worse operation characteristics and rapid device degradation.