High-power ultra-fast single- and multi-mode quantum-dot lasers with superior beam profile

Universal self-organization on surfaces of semiconductors upon deposition of a few non-lattice-matched monolayers using MOCVD or MBE leads to the formation of quantum dots (QDs). Their electronic and optical properties are closer to those of atoms than of solids. We have demonstrated for QD lasers a record low transparency current density of 6 A/cm² per QD layer at 1.16 μm, high power of almost 12 W, an internal quantum efficiency of 98%, and an internal loss below 1.5 cm^-1. Relaxation oscillations indicate the potential for cut-off frequencies larger than 10 GHz. GaAs-based QD lasers emitting at 1.3 μm exhibit an output power of 5 W and single transverse mode operation up to 300 mW. At 1.5 μm again an output power of 5 W has been obtained for a first device showing a transparency current of 70 A/cm ² per QD layer. Single-mode lasers at 1.16 and 1.3 μm show no beam filamentation, reduced M², reduced sensitivity to optical feedback by 30 dB and lower α-parameters as compared to quantum-well lasers. Passive mode-locking of 1.3 μm QD lasers up to 35 GHz is obtained. Error-free data modulation up to 5 Gb/s is shown, likely limited by RC parasitics only. Thus GaAs-based lasers are now close to replacing InP-based ones at least in the range up to 1.3 μm, probably up to 1.55 μm.