The present status of high-T_csuperconducting terahertz emitters

Abstract

A terahertz (THz) wave emitter using the stack of intrinsic Josephson junctions present in the high-Tc superconductor Bi2Sr2CaCu2O8+δ (Bi2212) has been developed. By applying a dc voltage V across the stack, the ac-Josephson effect converts this to an ac-current that emits photons at the Josephson frequency proportional to V. The Bi2212 device also behaves as and electromagnetic (EM) cavity, so depending upon the shape of the Bi2212 crystal, when the Josephson frequency matches that of a cavity resonance, the emission power is enhanced. However, the EM radiation characteristics also strongly depend upon the effects of Joule self heating of the device. In order to alleviate this Joule heating problem, we fabricated three distinct stand-alone Bi2212 sandwich device shapes, each crystal being first covered with Au on its top and bottom, and then sandwiched between sapphire plates. From our comparative studies of the three devices, we obtained important clues that could help to increase the emission power up to ∼mW and the frequency range up to several THz, as necessary for many applications such as security screening, high speed communications, medical and biological sensing, and astronomical detection, etc.

Microwave emission from superconducting vortices in Mo/Si superlattices

“…Later on, after the discovery of layered high-temperature superconductors, it has been recognized that Bi- and Tl-based cuprates with weakly coupled superconducting layers represent stacks of intrinsic Josephson junctions on the atomic scale 4 . Many Josephson junction-related effects have been observed in these systems, including terahertz emission 5 , 6 , Shapiro steps in the I – V curve induced by external microwave radiation 7 , 8 , Fiske resonances 9 , and oscillations of the critical current on the in-plane dc magnetic field. Current state-of-the-art Josephson flux-flow oscillators, which are used, e.g., in receivers in astrophysics, deliver microwatt powers at frequencies of 400–600 GHz and free-running emission linewidths as low as 0.6 MHz 10 – 12 .…”

Compact High- Tc Superconducting Terahertz emitter operating up to 86 K

“…[1,2]. As compact solid-state devices, intrinsic Josephson-junction (IJJ) stacks made of the high-criticaltemperature (T c ) superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO) have attracted much attention due to their potential to radiate especially at subterahertz frequencies [3][4][5], and intensive experimental and theoretical research has been performed. The possibility to perform terahertz imaging [65][66][67][68] and gas detection [69] or to realize an all-high-T c integrated receiver [70] has been demonstrated.…”

Study of Radiation Characteristics of Intrinsic Josephson Junction Terahertz Emitters with Different Thickness of Bi2Sr2CaCu2O8+δ Crystals

“…Using these THz emitters, several demonstrations of THz imaging and THz spectroscopy based on the Bi2212-THz emitters were performed [ 39 , 45 , 46 , 47 , 48 , 49 ]. More detailed characteristics of Bi2212-THz emitters have been reviewed in several papers [ 50 , 51 , 52 , 53 , 54 ].…”