Highly efficient one-dimensional quasi-crystalline THz semiconductor lasers

By lithographically patterning a sequence of air slits with different widths, following the Octonacci sequence, on the top metal layer of a double-metal quantum cascade laser, we demonstrate highly efficient surface emission at THz frequencies. The proposed versatile design allows either single-frequency-mode or multimode emission over a 530 GHz bandwidth, with peak optical powers of 240 mW (190 mW) in multimode (single-frequency-mode), record slope efficiencies up to ≈ 570 mW/A at 78 K and ≈ 720 mW/A at 20 K and wall-plug efficiencies η ≈ 1%.