The observations that led to the path-breaking first image of a black hole, from the Event Horizon Telescope Collaboration, were made in the terahertz band. [Event Horizon Telescope Collaboration]
Terabit/second wireless data links, hidden-object inspection, chemical-fingerprint identification, space exploration—these are some of the many applications for terahertz (THz) radiation that can reshape how we live in the coming decades. Bringing these applications to daily use, though, urgently requires bright coherent sources to empower THz systems. And the biggest challenge for such systems is boosting THz powers and frequency-sweeping ranges.