High performance operation of Terahertz Quantum Cascade Lasers – HI-TEQ

The terahertz (THz) frequency range, which is situated between the microwave and mid-infrared ranges, offers unique applications in various domains from medical and security imaging to the detection of gases. Even with these possibilities, the THz range remains largely unexplored due to the high cost, limited performance and dimensions of the source and detectors used until now. This is the “THz gap”, referencing to the lack of semiconductor based technologies.
In this context, a breakthrough in source technology was realised a few years ago with the THz Quantum Cascade Laser (QCL). This III-V based source is very promising as a practical THz source as it is based on standard semiconductor materials, powerful and extremely compact. The developments in this field have been rapid with good output powers and temperature operation above cryogenic temperatures. In spite of these efforts in performance development, however, the main obstacles in further improvements are due the complexity of the nanostructure, limitations in current QCL designs and the lack of control and comprehension of the underlying physics. In the present project we have investigated this bottleneck and demonstrated state-of-the-art THz QCL's performances as well as bringing new functionalities to these devices through its unique gain dynamics.
This project has united several domains for the successful implementation of the objectives; new QCL bandstructure designs; world-class material growth; new detection methods to characterize the gain and ultrafast response; extensive electromagnetic simulations of the waveguide geometry; and theoretical modeling of the QCL's lifetimes and transport properties.