Impact of temperature-induced optical wavelength detuning on the quantum dot distributed feedback lasers

In this work, we experimentally investigate the static characteristics, optical noise and feedback dynamics of quantum dot distributed feedback (QD DFB) lasers over a temperature range from 20^∘C to 85^∘C. Our results reveal that laser performance is closely related to the value of optical wavelength detuning (OWD) between the material gain peak and the lasing wavelength. A smaller OWD leads to significant overall performance enhancements. At 20^∘C, the laser exhibits a large OWD of 21.9 nm, corresponding to a higher relative intensity noise (RIN) of −132.5 dB/Hz and a spectral linewidth of 35.6 MHz. Furthermore, when the feedback strength exceeds −16.7 dB, the laser shows a slight degradation in stability, evidenced by a broadened radio-frequency spectrum and a gradual decrease in side-mode suppression ratio. As the temperature increases above 55^∘C, the OWD gradually decreases toward zero, resulting in improved noise characteristics (RIN ≈ −149 dB/Hz) and a dramatic linewidth reduction by nearly three orders of magnitude. Under these conditions, the laser also maintains stable operation even under strong optical feedback of −5.8 dB. Through comprehensive analysis, the optimal operating temperature is identified to be around 70^∘C, where the OWD approaches zero. This study comprehensively reveals the profound impact of OWD on the characteristic metrics and feedback dynamics of QD DFB lasers across a wide temperature range, providing valuable insights for designing temperature-insensitive and isolator-free semiconductor laser sources for advanced photonic systems.