The steady state and transient behavior of indium arsenide quantum dot laser diodes

Semiconductor quantum dots having carrier confinement in all three directions have long been predicted to be a superior semiconductor laser active region because of the unique electronic states in the quantum dots. The work presented in this dissertation describes improvements in the continuous-wave lasing performance of quantum dot lasers using the dots-in-a-well structure and an extensive study of the large signal transient properties of these lasers. These studies lead to further gains in the understanding of the device physics of these lasers.; The continuous wave characteristics of oxide-confined lasers with dots-in-a-well structure were investigated. For operation near 1.3 μm, very low threshold current densities (24 A cm−2), high external efficiencies (55%), very low internal loss (0.77 cm−1), and high operating temperature (up to 100°C) were achieved in the oxide-confined lasers. In addition, long wavelength oxide-confined two-section quantum dot lasers with an integrated intracavity absorber were fabricated using the dots-in-a-well structure. Clear bistability and hysteresis were observed in the electrical and optical characteristics of these devices. The origin of the bistable operation was identified and the properties of the quantum dot layer as a saturable absorber were investigated for the first time.; Using these two-section lasers, Q-switching and passive mode-locking were demonstrated for the first time in a quantum dot laser with a quantum dot saturable absorber. Q-switching operation up to 1 GHz has been achieved and the dependence of the Q-switched pulse parameters on the bias conditions was studied. Fully mode locked pulses at a repetition rate of 7.4 GHz with a width of about 17 ps were observed under the appropriate operating conditions. Important factors determining the pulse parameters in the mode-locked quantum dot lasers were identified.; Finally, a comprehensive rate equation model for the dots-in-a-well structure was proposed based on a realistic depiction of the electronic states. The model was then used to simulate the steady state characteristics and turn-on behavior of the quantum dot lasers, the gain and absorption saturation behavior of the dots-in-a-well structure, and the steady state bistable behavior and Q-switched operation of the two-section laser. Comparisons between the simulations and the experimental results have been made, improving our understanding of the physical processes occurring in quantum dot lasers.