Waveguide Embedding of a Double-Metal 1.9-THz Quantum Cascade Laser: Design, Manufacturing, and Results

We present the details of a coupling structure to embed a 1.9-THz double-metal quantum cascade lasers (QCLs) into a 120-μm-wide full-height rectangular waveguide. We describe the split-block manufacturing of the waveguide coupler together with a diagonal feed horn and present power and beam shape measurements of two different devices. The two devices differ in coupling factor, which can be chosen in a wide range by the mounting position of the QCL. Our waveguide embedding allows coupling of a large fraction of the laser power into the waveguide and the subsequent horn antenna emitting with a large Gaussian mode content, enabling efficient integration into a diffraction limited optics setup. This is illustrated by a self-mixing experiment and by using the embedded QCL as a local oscillator in a heterodyne receiver.