λ/4 phase-shifted distributed feedback lasers with chirped grating: dynamic single-mode and modulation characteristics analyses

The dynamic single-mode and modulation performance of λ/4 phase-shifted distributed feedback laser diode with chirped grating (QWS-CG-DFB) are analyzed theoretically. The numerical simulation shows that, In contrast to purely QWS-DFB laser, the enhanced dynamic single-mode suppression ratio (SMSR) can be reached by QWS-CG-DFB laser; Under the smaller biasing current, the modulation band-width in presence of chirped grating is narrower, this difference shrinks for larger biasing current; For large signal modulation, the chirped grating is helpful to increase the output extinction ratio, but worsens the frequency chirping.