| The quantum cascade laser is a new type of mid- and far-infrared semiconductor laser. Through quantum mechanical "bandgap engineering", an intersubband laser can be designed within the conduction band of an arbitrary semiconductor heterostructure. The goal of this work is to develop a compact infrared laser that is clearly superior to its' competitors, and is capable of deployment in a variety of advanced infrared systems. Inside this thesis, this topic will be explored in detail.; First, the relevant theoretical basis for an intersubband laser is presented, along with a suitable semiconductor basis for constructing such a laser. Next, material growth and characterization using gas-source molecular beam epitaxy is discussed in detail, including complete laser structure realization and optimization. Fabrication technology for quantum cascade lasers is then explored, which roughly follows the chronological evolution of processing innovations. Finally, laser testing and results are described in detail. The culmination of this work includes world record performance in a number of areas including: peak output power, average output power, slope efficiency, and threshold current density. |
