Quantum dot lasers: temperature insensitive operation and the prospect for high speed modulation

Because they operate on discrete electronic levels, quantum dot (QD) lasers offer the potentials for very high speed, temperature insensitive threshold, very low threshold current density, and low chirp modulation. In addition, self-organized QDs provide a greater range of wavelength operation in a given material system because greater strain, and therefore a greater range of material composition, can be accommodated in the crystal without the creation of dislocations. This has enabled GaAs-based lasers that operate at 1.3 μm, and also appears suited for GaAs-based lasers that operate at 1.55 μm. And because QDs confine excitons to dimensions of ∼10 nm or so, this novel active material is a key for photonic devices based on photonic crystals and microcavities. To date QD devices have only partially fulfilled their promise for a revolutionary new type of laser technology. This paper is aimed at explaining why QD lasers have yet to live up to their expectations, and how present approaches may be modified to greatly improve their performance.