On phase‐shift position and linewidth of λ/4‐shifted DFB laser diodes

Abstract The phase‐shift position (PSP) of a λ/4‐shifted distributed feedback (DFB) laser diode affects many characteristics of the laser. In particular, the effects of PSP on stability and external differential quantum efficiency for single longitudinal mode (SLM) operation of the laser were investigated previously by many authors. In this letter, a theoretical analysis of the effect of PSP on the spectral linewidth of the laser is presented. The results revealed the necessity of trade‐off in optimizing the PSP for a laser diode with a narrow linewidth while maintaining a sufficient stability and efficiency.