High Power Quantum Cascade Lasers for Terahertz Applications

It is here proposed to investigate quantum cascade laser technology for THz (0.3 - 7.5 THz) applications. Various material systems based on InP and GaAs will be studied theoretically and experimentally with respect to their suitability for laser growth. Material growth, following the design, will be done in-house using gas-source molecular beam epitaxy. Material characterization will be used to optimize growth conditions for the best material quality and to confirm layer thickness and interface quality. A self-consistent theory will be developed in order to explain and predict the behavior of arbitrary long wavelength intersubband devices. The focus of the theory will be to come up with design rules for a structure capable of high power, high temperature operation. At the end of this work, we will also propose a waveguide and thermal design for high power THz emission. THz imaging has already shown itself to be a powerful tool for homeland security. The ability to nondestructively evaluate package contents without using harmful x-ray radiation is extremely valuable. Further, terahertz sources may be useful in the field for other applications including communications and spectroscopy. This project will provide applied research into the theoretical and material-related design parameters for a THz quantum cascade laser. This source, once developed, will provide a compact source of high intensity, coherent THz radiation which can then be incorporated into a variety of security, communication, and spectroscopy systems.