Top: A scanning electron microscope image of a high-power surface-emitting terahertz semiconductor laser with hybrid gratings. Multiple lasers are fabricated on a Gallium Arsenide semiconductor chip. Each laser is approximately 1.5mm long, 10 microns thick and varies in width between 0.1mm to 0.2mm.
Bottom: Artistic illustration of the terahertz laser in operation. The laser's semiconductor material is sandwiched between metallic layers on both top and bottom. A periodic grating is introduced in the top metallic layer in the form of apertures from where light could leak out. An interplay of second- and fourth-order Bragg gratings (manifested as alternating single and double slits) leads to intense radiation from alternating periods of the periodic structure, combining coherently into a high quality single-lobed laser beam in the surface-normal direction.