Monolithically integrated electrically pumped terahertz scalar vortex lasers

Abstract

We report monolithically integrated, electrically pumped terahertz (THz) scalar vortex lasers based on a metal–metal waveguide platform. Each device integrates a distributed-feedback THz quantum cascade laser, a tapered transmission waveguide, and a scalar vortex emitter defined by a fork grating patterned in the top metallization. Designed using computer-generated holography, the fork grating enables controlled diffraction of the deeply subwavelength guided THz mode while preserving its uniform amplitude and planar traveling-wave phase front, thereby generating a well-defined helical phase in the emitted field. The devices directly emit scalar vortex beams at 3.4 THz with defined topological charges from −2 to +2, delivering pulsed output powers up to 16 mW under stable single-mode operation and exhibiting linear polarization with vortex-mode purity of 85.8%–91.7%. These results demonstrate compact and fully integrated THz vortex sources, providing a practical route toward on-chip generation of structured THz radiation.