Emission of Coherent THz Radiation from Superconductors

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 Bi 2 Sr 2 CaCu 2 O 8 . 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~50 kelvin. These results should stimulate the development of superconducting compact sources of THz radiation.

Direct observation of tetrahertz electromagnetic waves emitted from intrinsic Josephson junctions in single crystalline Bi2Sr2CaCu2O8+

“…An interesting characteristic feature of this EM emission lies in a monochromatic spectrum [1,2]. The line width is so sharp that the observed line width of radiation is limited by the resolution of our conventional spectrometers which has 0.25 cm À1 .…”

“…Recently, we have succeeded in generating intense, coherent, continuous and monochromatic electromagnetic (EM) waves in the THz frequency region emitted from the mesa structure fabricated on the single crystalline high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8+d , which is known as a typical intrinsic Josephson junction system [1,2]. Here, we provide further detailed information on such fascinating phenomenon generating EM waves at THz frequencies mainly from experimental point of view in order to make it clear the mechanism of the emission.…”

Zero-Field Fiske Resonance Coupled with Spin-Waves in Ferromagnetic Josephson Junctions

“…Furthermore, in the non-uniform S/FI/S junction, several applications such as spin-current emitter by utilizing spin-wave excitation in the FI 41 may be also possible in analogy with the emission of coherent THz radiation in the high-T c cuprate, [42][43][44] 7/10…”

“…In fact, the inhomogeneity of the junction was one of essential factors to realize the emission without external magnetic field. [42][43][44] However, novel devices using the S/FI/S junction are beyond the scope of the present paper and will be studied elsewhere.…”

Area dependence and influence of crystal inhomogeneity on superconducting properties of Bi2212 mesa structures

“…The frequency and the junction voltage proportionality is a promising fact for the design of frequency-tunable radiation sources. Ozyuzer et al successfully [6] observed directly the strong emission of electromagnetic waves using a mesa of Bi2212 crystal in the absence of an external magnetic field; the mesa shaped THz device with sizable power works as a dc voltage to high frequency converter.…”