Effect of temperature and ridge-width on the lasing characteristics of InAs/InP quantum-dash lasers: A thermal analysis view

•Thermal resistance of InAs/InP Qdash laser is obtained for different ridge-widths.•The essence of thermal effect on the broadband lasing characteristics is discussed.•Junction temperature rise is found to effect the spread of carriers in the medium.•Thermionic activation and phonon-assisted tunneling attributed probable mechanisms.•Injection locked Qdash laser as a source in optical communications is demonstrated. We investigate the thermal characteristics of multi-stack chirped barrier thickness InAs/InGaAlAs/InP quantum-dash-in-a-well lasers of different ridge widths 2, 3, 4 and 15µm. The effect of varying this geometrical parameter on the extracted thermal resistance and characteristic temperature, and their stability with temperature are examined. The results show an inverse relation of ridge-width with junction temperature with 2µm device exhibiting the largest junction temperature buildup owing to an associated high thermal resistance of ∼45°C/W. Under the light of this thermal analysis, lasing behavior of different ridge-width quantum-dash (Qdash) lasers with injection currents and operating temperatures, is investigated. Thermionic carrier escape and phonon-assisted tunneling are found to be the dominant carrier transport mechanisms resulting in wide thermal spread of carriers across the available transition states of the chirped active region. An emission coverage of ∼75nm and 3dB bandwidth of ∼55nm is exhibited by the 2µm device, thus possibly exploiting the inhomogeneous optical transitions to the fullest. Furthermore, successful external modulation of a single Qdash Fabry-Perot laser mode via injection locking is demonstrated with eye diagrams at bit rates of 2–12Gbit/s incorporating various modulation schemes. These devices are being considered as potential light sources for future high-speed wavelength-division multiplexed optical communication systems.