A spatium amplifier includes a plurality of amplifiers connected between a pair of spatial couplers, each having a core member and a shell member forming an antenna. The core member includes a cylindrical core portion and a plurality of tapering core fins extending radially outwardly from the cylindrical core portion. The shell member includes a cylindrical shell portion and a plurality of tapering shell fins extending radially inwardly from the cylindrical shell portion to form a plurality of fin pairs. Each fin pair forms a tapering channel having a first channel height at a first end of the antenna and a second channel height larger than the first channel height at a second end of the antenna. Each of the plurality of amplifiers is electromagnetically coupled to a respective fin pair at the first end of each of the antennas.