Far-field engineering of metal -metal terahertz quantum cascade lasers with integrated horn antennas

The far-field of metal-metal terahertz quantum cascade lasers is greatly improved through integrated and stable planar horn antennas on top of the QCL ridge. The antenna structures introduce a gradual change in the high modal confinement of metal-metal waveguides and permit an improved far-field, showing a five times increase in the emitted output power. The two dimensional far-field patterns are measured at 77K and compared to electromagnetic simulations. The influence of parasitic high order transverse modes are restricted through the engineering of antenna structure (ridge and antenna width) to couple out the fundamental mode only.