Terahertz-wave emission from Bi2212 intrinsic Josephson junctions: a review on recent progress

Abstract

Emission of terahertz (THz) electromagnetic (EM) waves from a high critical temperature (Tc) superconductor intrinsic Josephson junction (IJJ) is a new and promising candidate for practical applications of superconducting devices. From the engineering viewpoint, the IJJ THz source is competitive against the present semiconducting THz sources such as quantum cascade lasers and resonance tunnelling diode oscillators because of its broad tunable frequency range and ease of the fabrication process for the device. The emitted EM waves are considered to be coherent because the emission is yielded by synchronisation of thousand stacked IJJs consisting of the mesa device. This synchronisation is peculiar: the resonant frequency of each IJJ is distributed because the cross section of the mesa device is trapezoidal in shape. One of the key features of the synchronisation mechanism is the temperature inhomogeneity of the emitting device. In this topical review, we describe the recent progress in studies of IJJ THz sources with particular emphasis on the relevance of the temperature inhomogeneity to the synchronisation and the emission intensity. This review is of specific interest because the IJJ THz source shows the rich variety of functions due to self-heating which has always been a detrimental feature in the present superconducting devices. Moreover, the thermal managements used for IJJ THz sources will be common with those of other semiconducting devices such as quantum cascade lasers. In addition, this review is to invite the readers into related research through the detailed descriptions of experimental procedures.

Josephson emission with frequency span 1–11 THz from small Bi2Sr2CaCu2O8+δ mesa structures

“…Superconducting Josephson junctions allow a direct conversion of DC-voltage into high-frequency electromagnetic oscillations with a tunable frequency 9–13 Here V is the voltage per junction, e —electron charge and h —Plancks constant. The frequency is limited only by the superconducting energy gap, which is sub-THz for low- T c 10 and ≥10 THz for high- T c superconductors 14 .…”

Monolithic Superconducting Emitter of Tunable Circularly Polarized Terahertz Radiation

“…The highest degree of circular polarization (DOCP) recorded in the study proposed herein is 99.7%, which is higher than that recorded by state-of-the-art quantum cascade lasers used for obtaining circular polarization [9,10,27]. As circularly polarized THz waves could be employed in a wide variety of potential applications, the result obtained in this study, along with recently reported packaging [28] and demonstration of THz torch [29], it is believed, will significantly influence and inspire the development of practical applications of IJJ-based THz emission devices [4,30].…”

“…This is largely because of the numerous vibrational and rotational molecular absorption lines it contains which are used as marking regions in spectroscopy applications [1]. Ever since the demonstration of an intense THz radiation from a stack of intrinsic Josephson junctions (IJJs) made from Bi2Sr2CaCu2O8+δ (Bi-2212) [2], there has been an increased interest in the development of IJJ-based devices as highly promising emitters of coherent continuous-wave terahertz radiations [3][4][5]. Imaging, sensing, and spectroscopy applications require some control over the properties of radiations emitted from THz sources.…”

“…Circularly polarized THz emissions have recently been experimentally achieved by utilizing monolithic devices, such as quantum cascade lasers [9,10] and resonanttunneling diodes [11]. Compared to these devices, IJJ-based sources can cover wider frequency ranges, which are unattainable by other THz sources [4]. Furthermore, the emission intensity of IJJ-based devices can also be thermally controlled, both internally [12,13] and externally [14,15].…”

Dynamic Stimulation of Superconductivity With Resonant Terahertz Ultrasonic Waves

“…An equally important aspect of the experiment is the tunable THz source, and how the THz signal is coupled to the piezoelectric substrate. A leading candidate for a tunable THz source is an intrinsic Josephson junction (IJJ) stack, consisting of a single crystal of the cuprate BSCCO [40]- [42]. Fig.…”