“…There are a variety of advances of QD active medium compared to the quantum well (QW) medium such as ultralow threshold current density [1, 2] (including an important 1.3µm telecommunication wavelength region), high thermal stability [3], and high-speed modulation [4,5]. Recently, a high gain multi-layer QD (MQD) medium in vertical cavity surface emitting lasers (VCSELs) with doped distributed Bragg reflectors (DBRs) was successfully demonstrated [6,7,8,9].…”