In a recent pioneering work,† phase-resolved measurements of a THz QCL structure were performed using ultrafast pulses. This powerful method probes the dynamics of QCL structures in a time- and phase-resolved fashion, directly measuring important properties such as gain and loss.
In this project, we extend the previous work to THz QCLs based on metal-metal waveguides, and investigate a variety of gain media including resonant-tunneling and scattering-assisted injection schemes. The key enabling element is a monolithically integrated TDS emitter that efficiently generates and emits THz pulses into the quantum structures to be investigated. Such an integrated emitter will also allow future integration of lumped THz devices (for example, transistors) and distributed amplifiers based on THz QCL gain medium.