Guiding a terahertz quantum cascade laser into low-loss hollow waveguides
We demonstrate that azimuthally polarized micro-ring THz quantum-cascade lasers can be coupled to hollow metallic waveguides with efficiencies ≥96% and perfectly matched with the TE01 waveguide mode, giving attenuation losses < 3dB/m. The use of Ag coated-flexible pipe waveguides allows propagation of either vertically polarized or azimuthally polarized QCL beams with propagation losses as low as 2.1–4.4 dB/m and bending losses lower than 1.2 dB.