Theory for the spectral linewidth of passive-coupled-cavity semiconductor lasers

A simple expression for the spectral linewidth of passive-coupled-cavity (PCC) semiconductor lasers is presented. Experimentally observed linewidth narrowing and periodic variation of the linewidth as functions of the injection current and the gap between the active cavity (laser) and the passive cavity (graded index, or GRIN rod) can be satisfactorily explained by this formula.<
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