Owing to their high integration and functionality, nanometer-scale optoelectronic devices based on III-V semiconductor materials are emerging as an enabling technology for fiber-optic communication applications. Semiconductor quantum dots (QDs) with the three-dimensional carrier confinement offer potential advantages to such optoelectronic devices in terms of high modulation bandwidth, low threshold current density, temperature insensitivity, reduced saturation fluence, and wavelength flexibility. In this paper, we review the development of the molecular beam epitaxial (MBE) growth methods, material properties, and device characteristics of semiconductor QDs. Two kinds of III-V QD-based lasers for optical communication are summarized: one is the active electrical pumped lasers, such as the Fabry–Perot lasers, the distributed feedback lasers, and the vertical cavity surface emitting lasers, and the other is the passive lasers and the instance of the semiconductor saturable absorber mirrors mode-locked lasers. By analyzing the pros and cons of the different QD lasers by their structures, mechanisms, and performance, the challenges that arise when using these devices for the applications of fiber-optic communication have been presented.

The modulation p-doping technique has emerged as an effective way to optimize the carrier dynamics process of quantum dot (QD) structures. Here, the laser structures based on the 1.3 μm multiple-layer InAs/GaAs QD were fabricated with and without modulation p-doping. The carrier relaxation rate was increased after modulation p-doping, as demonstrated by transient absorption spectroscopy. The higher relaxation rate in p-doped QDs could be explained by more rapid carrier–carrier scattering process originating from increasing of the hole quasi-Fermi-level movement that increases the probability of occupancy of the valence states. In addition, the lasing behavior of Fabry–Perot lasers with and without modulation p-doping was investigated and compared. It was found that the ground state (GS) lasing in the absence of facet coating was successfully achieved in a p-doped laser diode with short cavity length (400 μm), which can be attributed to the higher GS saturation gain caused by p-doping. With assistance of a designed TiO2/SiO2 facet coating whose central wavelength (∼1480 nm) is far beyond the lasing wavelength of 1310 nm, the GS lasing could be realized in a laser diode with short cavity lengths (300 μm) under continuous wave operation at room temperature, implying great potential for the development of low-cost and high-speed directly modulated lasers.

Semiconductor superluminescent light-emitting diodes (SLEDs) have emerged as ideal and vital broadband light sources with extensive applications, such as optical fiber-based sensors, biomedical sensing/imaging, wavelength-division multiplexing system testing and optoelectronic systems, etc. Self-assembled quantum dots (SAQDs) are very promising candidates for the realization of broadband SLED due to their intrinsic large inhomogeneous spectral broadening. Introducing excited states (ESs) emission could further increase the spectral bandwidth. However, almost all QD-based SLEDs are limited to the ground state (GS) or GS and first excited state (ES1) emission. In this work, multiple five-QD-layer structures with large dot size inhomogeneous distribution were grown by optimizing the molecular beam epitaxy (MBE) growth conditions. Based on that, with the assistance of a carefully designed mirror-coating process to accurately control the cavity mirror loss of GS and ESs, respectively, a broadband QD-SLED with three simultaneous states of GS, ES1 and second excited-state (ES2) emission has been realized, exhibiting a large spectral width of 91 nm with a small spectral dip of 1.3 dB and a high continuous wave (CW) output power of 40 mW. These results pave the way for a new fabrication technique for high-performance QD-based low-coherent light sources.