High-speed mode-locked quantum-dot lasers and optical amplifiers

Recent results on GaAs-based high-speed mode-locked quantum-dot (QD) lasers and optical amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex dependence on device and operating parameters is discussed on the basis of experimental data obtained with integrated fiber-based QD device modules. Hybrid and passive mode locking of QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultralow timing jitter down to 190 fs, high output peak power beyond 1 W, and suppression of Q-switching are reported, showing the large potential of this class of devices for O-band optical fiber applications. Results on cw and dynamical characterization of QD semiconductor optical amplifiers (SOAs) are presented. QD amplifiers exhibit a close-to-ideal noise figure of 4 dB and demonstrate multiwavelength amplification of three coarse wavelength division multiplexing (CWDM) wavelengths simultaneously. Modelling of QD polarization dependence shows that it should be possible to achieve polarization insensitive SOAs using vertically coupled QD stacks. Amplification of ultrafast 80 GHz optical combs and bit-error-free data signal amplification at 40 Gb/s with QD SOAs show the potential for their application in future 100 Gb Ethernet networks.