0.43 THz emission from high-T(c) superconducting emitters optimized at 77 K

Area of Science:

• Condensed Matter Physics
• Superconductivity
• Terahertz Technology

Background:

• Traditional terahertz (THz) radiation systems often require liquid helium for cooling, limiting their compactness and practicality.
• High-temperature superconductors offer potential for THz devices operating at more accessible temperatures.
• Reducing Joule heating in superconducting devices is crucial for stable and efficient operation.

Purpose of the Study:

• To develop a compact, continuous-wave sub-terahertz radiation system that operates without liquid helium.
• To achieve the highest possible emission frequency at 77 K using a superconducting device.
• To demonstrate broad tunability of the THz emission frequency.

Main Methods:

• Fabrication of a rectangular mesa device from a high-T(c) superconducting Bi2Sr2CaCu2O(8+δ) single crystal.
• Implementation of a novel stand-alone mesa sandwich structure to minimize dc-current Joule heating.
• Thermal connection of the mesa to sapphire plates using thermal grease with embedded diamond nano-crystals.
• Operation and testing within a liquid nitrogen (77 K) environment and a He-flow cryostat for temperature variation.

Main Results:

• Successful operation of a liquid helium-free sub-terahertz radiation system at 77 K.
• Emission of intense radiation at 0.437 THz, the highest frequency reported for a device operating at 77 K.
• Demonstration of broad frequency tunability from 0.31 THz (at 79 K) to 1.31 THz (at 30 K) by varying bias current and temperature.

Conclusions:

• The developed system represents a significant advancement in compact and practical THz radiation sources.
• The novel mesa design effectively reduces Joule heating, enabling higher frequency operation at accessible temperatures.
• The broad tunability makes this superconducting THz source a promising candidate for various spectroscopic and imaging applications.