Quantum dots: lasers and amplifiers

Abstract

Continuous wave room-temperature output power of ∼ 3 W for edge emitters and of 1.2 mW for vertical-cavity surface-emitting lasers is realized for GaAs-based devices using InAs quantum dots (QDs) operating at 1.3 µm. Characteristic temperatures up to 170 K below 330 K are realized. Simultaneously, differential efficiency exceeds 80% for these devices. Lasers emitting up to 12 W at 1140–1160 nm are useful as pump sources for Tm3+-doped fibres for frequency up-conversion to 470 nm. Both types of lasers show transparency current densities of 6 A cm−2 per dot layer, ηint = 98% and αi around 1.5 cm−1. Long operation lifetimes (above 3000 h at 50 °C heatsink temperature at 1.5 W CW) and improved radiation hardness as compared to quantum well (QW) devices are manifested. Cut-off frequencies of about 10 GHz at 1100 nm and 6 GHz at 1300 nm and low α factors resulting in reduced filamentation and improved M2 values in single-mode operation are realized. Quantum dot semiconductor optical amplifiers (QD SOAs) demonstrate gain recovery times of 120–140 fs, 4–7 times faster than bulk/QW SOAs. The breakthrough became possible due to the development of self-organized growth in QD technology.