Multi-cavity terahertz quantum cascade lasers

In this contribution, we demonstrate the detection capability of the quantum cascade laser (QCL) active region and show the flexibility of a multi-section THz QCL. The laser waveguide is split into two sections. The first section is intended as a detector element, capable of monitoring THz radiation in the laser cavity. The remaining section is driven independently, so different operation modes can be set. The electrical decoupling is achieved by a 3 μm wide gap between individual sections, preserving sufficient optical coupling.