A Broadband Polarization-Rotating Vivaldi Antenna for Beam Focusing of Terahertz Quantum Cascade Lasers

Terahertz (THz) Quantum Cascade Lasers (QCLs) have been of large interest in the context of very broadband and compact frequency combs in the THz spectral range [1]. For THz QCLs, the double metal waveguide proved to be advantageous in terms of bandwidth, compactness and low dispersion. However, as it confines the optical mode to deeply subwavelength dimensions, the output beam is highly divergent, as displayed in Fig. 1(a). Previous solutions addressing this issue were either impractical or not so broadband [2,3]. To improve the far-field properties of the double metal waveguide across a very large frequency range, we designed, fabricated and characterized a broadband, narrow beam Vivaldi Antenna [4].