Tunable terahertz source on a chip with decade-long stability using layered-superconductor elliptical microcavities

Chip-scale, electrically tunable, continuous-wave, coherent terahertz (THz) radiation sources are critical for emerging applications in sensing, imaging, spectroscopy, communications, space, and quantum technologies. Here, we demonstrate a robust source-on-a-chip THz emitter based on a layered high-temperature superconductor, engineered with an elliptical microcavity and capable of sustained coherent emission over an unprecedented operational lifetime exceeding 11 years. This compact THz source operates up to 60 K (with <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>T</a:mi> <a:mrow> <a:mrow> <a:mi mathvariant="normal">c</a:mi> </a:mrow> </a:mrow> </a:msub> </a:math> ≈ 90 K), delivering stable radiation in the 0.7–0.8 THz range, with on-chip electrical tunability from 100 GHz to 1 THz. Coherence arises from the phase-locked oscillation of intrinsic Josephson junction arrays, resonantly coupled to transverse electromagnetic modes within the cavity, analogous to a laser cavity, yielding collective macroscopic oscillations. THz emission remains detectable across an approximately 0.5-m free-space open-air link at room temperature. We analyse the cavity-mode structure and extract THz photon generation rates up to approximately 503 photons <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:msup> <d:mi>fs</d:mi> <d:mrow> <d:mo>−</d:mo> <d:mn>1</d:mn> </d:mrow> </d:msup> </d:math> in cryogenic conditions and 50–260 photons <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:msup> <f:mi>ps</f:mi> <f:mrow> <f:mo>−</f:mo> <f:mn>1</f:mn> </f:mrow> </f:msup> </f:math> over the air. These results demonstrate, for the first time, sustained and electrically tunable coherent THz emission from superconductors over multiyear timescales, defining another class of robust, chip-integrated THz lasers with applications in scalable THz and quantum technologies.