Development of Quantum Dot Lasers for Data-Com and Silicon Photonics Applications

The device characteristics of semiconductor lasers have been improved with progress in active layer structures. Carrier confinement dimension plays an important role especially in temperature sensitivity as well as slope efficiency. Three-dimensional carrier confinement to nano-scale semiconductor crystal, known as “quantum dots (QDs)” had been predicted to show ultimately superior device performances. Self-assembly formed InAs QDs grown on GaAs had been intensively promoted in order to achieve QD lasers with superior device performances. Now high-density, high-optical quality QDs have been realized through improved molecular beam epitaxy growths and QD lasers with better temperature characteristics are in the stage of mass-production for a data-com market. Fabry-Perot type, as well as distributed feedback type QD lasers show quite improved laser characteristics. Also, the unique device characteristics of QD lasers opened new application fields such as the use for resource searching by utilizing high-temperature operation such as lasing at higher than 200 °C. For silicon-photonics, QD lasers are used as an optical source for athermal operation. In this paper, the evolution of QDs, as well as improved device performances for novel application fields are discussed.