Emission of Coherent THz Radiation from Superconductors

TLDR

Compact solid‑state THz sources are sought for sensing, imaging, and spectroscopy across physical and biological sciences. The study demonstrates that coherent continuous‑wave THz radiation of sizable power can be extracted from intrinsic Josephson junctions in the layered high‑temperature superconductor Bi₂Sr₂CaCu₂O₈. By exciting an electromagnetic cavity resonance inside the crystal, a macroscopic coherent state is generated in which many junctions synchronize in phase, analogous to a laser cavity. The emission power scales with the square of the number of synchronized junctions, reaching 0.5 µW at 0.85 THz and remaining detectable up to about 50 K, suggesting a viable route toward compact superconducting THz sources.

Abstract

Compact solid-state sources of terahertz (THz) radiation are being sought for sensing, imaging, and spectroscopy applications across the physical and biological sciences. We demonstrate that coherent continuous-wave THz radiation of sizable power can be extracted from intrinsic Josephson junctions in the layered high-temperature superconductor Bi2Sr2CaCu2O8. In analogy to a laser cavity, the excitation of an electromagnetic cavity resonance inside the sample generates a macroscopic coherent state in which a large number of junctions are synchronized to oscillate in phase. The emission power is found to increase as the square of the number of junctions reaching values of 0.5 microwatt at frequencies up to 0.85 THz, and persists up to approximately 50 kelvin. These results should stimulate the development of superconducting compact sources of THz radiation.