Dynamical Analysis of Terahertz Quantum Cascade Lasers

Abstract: This thesis focuses on various aspects in terahertz quantum cascade lasers such as high temperature performances, electrical instabilities and chaos. In the first part of the thesis, an introduction to the topic and the non equilibrium Green's function package applied is given with particular emphasise on the inhomogeneous domain model and the chaos theory. In addition, new results regarding the high temperature operation of low frequency terahertz quantum cascade lasers are presented. In the second part, the related research articles are shown. Paper I shows numerical simulations demonstrating the first autonomous terahertz quantum cascade laser exhibiting chaos. Paper II provides a detailed analysis of the current record-holding terahertz quantum cascade lasers operating around 4 terahertz. A new design is suggested which should operates at an even higher temperature of 265 K.Paper III analyses the spectral behaviour of the output light generated by oscillating field domains in direct cooperation with the experiment. The overall behaviour is related to the phenomenological boundary conductivity and the external capacitance.