Fig. 1

Resonator design and rationale. a Schematic diagrams of the laterally corrugated wire laser with a periodic (period Λ_fb = 13.6 µm) sinusoidal corrugation. The double-metal cavity comprises a central corrugated region, with two Cr pads at the ends of the resonator cavity being used to suppress unwanted electromagnetic modes. The inset shows the top metal contact (yellow) patterned with etched air holes (blue) with a periodicity Λ_e, which define the extraction wavevector k_e. Λ_e was varied in the range 19.4–23.7 µm, around the ideal theoretical value of 21.2 µm for an expected emission frequency of 3.1 THz. The thin Cr absorbing layer is marked in gray. b Light cone diagram. The feedback wavevector k_fb (red line) and the extraction one k_e (blue line) are indicated on the graph, together with the backward-propagating  (black line) and forward-propagating (green line) laser cavity wavevectors. For a given frequency ν, different η parameters provide distinct extraction wavevectors, which determine the light extraction efficiency and emission angle ϑ into free space (dotted blue line). Here n is the refractive index and c is the light speed in vacuum. c One-dimensional photonic band structure, computed on the feedback geometry only, based on a sinusoidal spatial profile of the dielectric function, and for a ridge having average width of 40 µm, a lateral corrugation length of Λ_fb = 13.6 µm, and a corrugation amplitude of 10 µm on each side of the mesa. d Scanning electron microscope image of a fabricated device, with hole radius, r = 5 µm, Λ_e = 22.4 µm (η = 0.95), and average width of 40 µm