Semiconductor quantum dot lasers

Quantum dot (QD) diode lasers attract currently much attention due to their ability to emit light in the advanced near-infrared region at extraordinarily low threshold current densities. A vertical-cavity surface emitting laser (VCSEL), having a superior beam quality, improved temperature stability, low threshold current, and cost-effective planar fabrication, is also an attractive device variant. Here we discuss the state of the art of these lasers intended for the use in 1.3-mu m fiber-optic communications. The discussion is centered on an InAs/GaAs semiconductor QD system. Basic issues of the QD synthesis in the system are addressed. The achievement of the control over the 1.3-mu m QD emission is demonstrated. Both, wide-stripe and single-mode edge-emitting lasers are described. The lasers designed have a very low threshold current density, high differential efficiency, and a high output power. Narrow-stripe 1.3-mu m QD lasers generate in a single mode, have a record-low threshold current, and produce the continuous-wave (CW) power output in excess of 100 mW. Also, we report on QD VCSELs emitting at 1.3 mu m. The design of their cavity and active region are described. The room-temperature CW output power of these lasers is as high as 2 mW. Both, the edge- and surface-emitting lasers satisfy the demands of the fiber optical communication technology.