Study on broadband emitting self-assembled quantum-dot material and devices

Self-assembled quantum dots (QDs) with broadband emitting spectra, QD superluminescent diodes (SLDs) and external cavity tunable QD laser have been studied. By optimizing growth parameters and sample structure of InAs QDs, up to 150-nm photoluminescence width is achieved. High-power InAs/GaAs QD-SLDs with the CW output power of 200 mW and the spectral bandwidth of near 60 nm have been obtained at room temperature. In addition, broadband emitting InAs/GaAs QD-SLDs are fabricated. The device exhibits properties of 110 nm bandwidth with the centre of 1.1 ¿m and above 30 mW output under pulsing injection at room temperature. By using InAs/AlGaAs QDs as active layers, we get SLDs with 142 nm spectral width. Broadband external cavity tunable laser has been constructed by using broad-emitting spectral InAs/GaAs QD gain device. Leaving the facets uncoated, a tuning range of 110 nm, which covers the ground state and the first excited state of the QDs, is realized. By the anti-reflectance coating on one facet, which is coupled with the grating, the tuning bandwidth is expanded to near 150 nm. The ground state, the first and second excited states of the QDs contribute to the broad tuning range.