The interplay of inhomogeneous and homogeneous broadening of InGaAs/GaAs quantum dot (QD) Fabry Perot laser is discussed by a comprehensive rate equation model. It is found that for a given inhomogeneous broadening, there is always an optimum homogeneous broadening which leads to a narrowest output power spectrum. With the optimum values, the single longitudinal mode laser is designed. For a cavity length of 200-m, a SMSR (side mode suppression ratio) of 41.65dB and 3dB bandwidth of 17GHz are obtained under 5mA driving current. Moreover, to get a SMSR over 38dB, the inhomogeneous broadening should be lower than 17meV. This work can provide a quantitative reference basis for the single mode quantum dot laser design.
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