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For the first time, distributed-feedback lasers emitting at 1625 nm with high output power and low operation current are fabricated. Temperature-induced performance degradation is minimised by optimising carrier and optical confinement. Consequently, these L-band lasers show no additional degradation in threshold current with rising temperature compared to C-band lasers.
Introduction: The demand for large-capacity optical communications based on wavelength division multiplexing (WDM) technology has been increasing. At present, C-band and L-band erbium-doped fibre amplifiers (EDFAs) having wavelength channel counts ranging from 80 to 160 per direction are utilised for long-distance transmission systems. As the number of wavelength channels and the system complexity increase, high-power dense WDM (DWDM) C- and L-band laser sources are very attractive in the sense that the losses in the system can be compensated without having to use optical amplifiers. In addition, low operation current is desirable to reduce power consumption and improve reliability of the laser sources.
To date, existing work on high-power continuous-wave (CW) distributed-feedback (DFB) lasers have focused on C-band [1-4].To the best of our knowledge, there have been no report on high-power L-band CW DFB lasers, except by us [5]. Hence, in this Letter we report details of the design and successful fabrication of high-power L-band DFB laser diodes that emit 106 mW of output power even at an emission wavelength of 1625 nm where Auger recombination has significant impact on semiconductor laser performances, such as poor slope efficiency and high threshold current [6].
Design considerations and laser structure: If the barrier composition for C-band lasers is used for designing L-band lasers, the large bandgap difference between well and barrier (DEg) causes non- uniform distribution of carriers to each quantum well. This has...