High-power, continuous, broadly tunable THz radiation from 0.29 to 1.06 THz, was obtained from the outer current-voltage characteristic (IVC) branch of a single stand-alone mesa of the high-transition temperature Tc superconductor Bi2Sr2CaCu2O8+δ. The particular metallic film structures placed both beneath and atop the mesas resulted in more efficient heat dissipation, higher allowed applied dc voltages, larger IVC loops, wider emission temperature ranges, and much broader emission frequency tunability than obtained previously.

Recent developments of coherent terahertz (THz) oscillators based on the intrinsic Josephson junctions (IJJs) in mesas of the high temperature superconductor Bi2Sr2CaCu2O8+δ are reviewed. Experimental and theoretical studies of the emission from equilateral, right-angled isosceles, and acute isosceles triangular mesas are compared with those obtained from rectangular, square, and disk mesas, in order to determine the role of the mesa geometry. The superconducting properties and emission frequency f spectra are presented for a variety of triangular mesa geometries. Analytic and finite difference time domain numerical calculations of the emissions from the internal electromagnetic (EM) cavity modes of triangular mesas are compared with experiment. The experimental f always satisfies the ac Josephson relation, and its narrow linewidth arises from the synchronized emissions from many IJJs. For some mesa geometries, f also strongly locks onto an EM cavity mode frequency, enhancing the emission’s stability and output power. For other geometries, such cavity mode locking is weak, and f is highly tunable.

A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-Tc superconductor Bi2Sr2CaCu2O8+δ was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications.

A reflection type of imaging system is shown at sub-terahertz frequencies generated from high-Tc superconducting intrinsic Josephson junction mesa structures fabricated by single crystalline Bi2Sr2CaCu2O8+δ to demonstrate how the sub-terahertz imaging technique using monochromatic radiation is powerful and unique for the variety of practical applications. Several examples are discussed in detail and are compared to other terahertz imaging systems.

In a previous our study, coherent and continuous electromagnetic radiation phenomena in mesa structures of Bi2Sr2CaCu2O8+δ single crystal have been investigated precisely in magnetic fields up to only 150 Oe. This experimental result showed that the emission intensity decreases sharply for the field parallel to the c-axis, while it decreases gradually as increasing magnetic field for the in-plane field. In order to improve the measurement, we developed a new system with a better angular resolution and much wider magnetic field range up to 6 T, and a mesa having much stronger THz emission power. The mesa structure is also changed to the stand-alone type of mesa, which produces higher power THz radiation with the ​ideal distribution of radiation. In this presentation, the recent detailed results will be shown in magnetic fields both parallel and perpendicular to the ab-plane of Bi2212, where the Josephson and pancake vortices are playing an important role for THz radiation. This work was supported in part by CREST-JST, WPI-MANA project (NIMS) and Strategic Initiative category (A) at the University of Tsukuba.

In order to determine if the mesa geometry might affect the properties of the coherent terahertz (THz) radiation emitted from the intrinsic Josephson junctions in mesas constructed from single crystals of the high-temperature superconductor, Bi₂Sr₂CaCu₂O₈+δ, we studied triangular mesas. For equilateral triangular mesas, the observed emission was found to be limited to the single mesa TM(1,0) mode. However, tunable radiation over the range from 0.495 to 0.934 THz was found to arise from an acute isosceles triangular mesa. This 47% tunability is the widest yet observed from the outer current-voltage characteristic branch of such mesas of any geometry. Although the radiation at a few of the frequencies in the tunable range appear to have been enhanced by cavity resonances, most frequencies are far from such resonance frequencies, and can only be attributed to the ac-Josephson effect.

In 2007 [1], we have succeeded in observing strong, coherent, and continuous THz emission from a mesa of Bi2Sr2CaCu2O8+s single crystal with a rectangular dimension of a few hundred micrometers in length, several tens of micrometers in width, and a few micrometers in thickness. Since then, great progress has been made both in understanding the fundamental mechanism of the radiation [2-6] and in practical applications [7-9]. Here, we show the present status of the THz radiation from high-Tc superconductor Bi2Sr2CaCu2O8+δ mesa structures in comparison with the other fast developing solid state THz sources such as resonant tunnelling diodes (RTD), uni-travelling carrier photodiodes (UTCP) and quantum cascade lasers (QCL), etc.

Tunable terahertz (THz) radiation emitted from the triangular mesa structures consisting of the intrinsic Josephson junctions in single-crystalline high-Tc superconducting Bi2Sr2CaCu2O8+δ is investigated using angular distribution measurements of the radiation power and Fourier transform infrared spectroscopy.

An attempt has been made to improve THz radiation characteristics emitted from mesas made from Bi2Sr2CaCu2O8+δ single crystals in order to achieve an ultimate goal of high frequency quantum device applications, named here as the Quantum Terahertz Electronics (QTE). Among many requirements to be fulfilled and necessary for the development, we here made an effort to generate more intense radiation using a stand-alone type of mesa. Some characteristic features are described.

We have measured the magnetic field effect of THz radiation emitted from a mesa structure fabricated from high-quality high-transition temperature (Tc) superconductor single crystalline Bi2Sr2CaCu2O8+δ using a newly developed measurement system in magnetic fields up to 6T. The results show that the THz radiation was strongly suppressed in magnetic fields with a considerable anisotropy: about 20Oe magnetic field is sufficient for the total suppression of the THz radiation for the field being parallel to the c-axis, while for the field being parallel to the ab-plane the radiation has first a slight hump at about 50Oe, then has a sudden drop at about 150Oe, and shows a step-wise structure between about 200 and 300Oe before the intensity diminishes completely below the detection sensitivity limit at about 450Oe. These characteristic features are discussed in comparison with recent theoretical works.

In 2007, the first observation of the coherent terahertz (THz) electromagnetic (EM) waves from mesa structures of intrinsic Josephson junctions (IJJs) in hi…This work has been supported in part by CREST-JST (Japan Science and Technology Agency), WPI-MANA project (NIMS).

Submitted for the MAR13 Meeting of The American Physical Society Magnetic field effects on THz radiation from Bi2Sr2CaCu2O8+δ mesa structures1 TAKEO KITAMURA, TAKANARI KASHIWAGI, MANABU TSUJIMOTO, KAVEH DELFANAZARI, MASASHI SAWAMURA, KAZUYA ISHIDA, SHUNSUKE SEKIMOTO, CHIHARU WATANABE, University of Tsukuba, TAKASHI YAMAMOTO, Japan Atomic Energy Agency, HIDETOSHI MINAMI, MASASHI TACHIKI, KAZUO KADOWAKI, University of Tsukuba — In a previous our study, coherent and continuous electromagnetic radiation phenomena in mesa structures of Bi2Sr2CaCu2O8+δ single crystal have been investigated precisely in magnetic fields up to only 150 Oe [1]. This experimental result showed that the emission intensity decreases sharply for the field parallel to the c-axis, while it decreases gradually as increasing magnetic field for the in-plane field. In order to improve the measurement, we developed a new system with a better angular resolution and much wider magnetic field range up to 6 T, and a mesa having much stronger THz emission power. The mesa structure is also changed to the stand-alone type of mesa, which produces higher power THz radiation with ideal distribution of radiation [2]. In this presentation, the recent detailed results will be shown in magnetic fields both parallel and perpendicular to the ab-plane of Bi2212, where the Josephson and pancake vortices are playing an important role for THz radiation. [1] K. Yamaki et al., physica C 470 (2010) S804. [2] T. Kashiwagi et al., Jpn. J. Appl. Phys. 51 (2012) 010113. 1This work was supported in part by CREST-JST, WPI-MANA project (NIMS) and Strategic Initiative category (A) at the University of Tsukuba. Takeo Kitamura University of Tsukuba Date submitted: 13 Nov 2012 Electronic form version 1.4

In order to understand the radiation observed from the intrinsic Josephson junctions in triangular Bi2Sr2CaCu2O8+δ mesas, we calculate the transverse magnetic (TM) electromagnetic modes for thin equilateral cavities. A new set of distinct but degenerate TM modes coexists with the known modes of Helszajn and James, but are expected to lead to distinct radiation angular distribution patterns. Although we have been unable to solve for the exact TM modes of a thin cavity of general acute isosceles triangular shape, we solved exactly the closely related problems of the TM cavity modes of two thin circumscribing “pie-shaped” wedges, which provide highly accurate approximations to very acute isosceles triangular cavities.

We report on intense, tunable, continuous, and coherent THz electromagnetic waves observed from differently shaped triangular mesas of the intrinsic Josephson junctions in single crystalline high-Tc superconducting Bi2Sr2CaCu2O8+δ. All samples are fabricated by focused ion beam milling.

We demonstrate an imaging system and use the high-Tc superconducting micro-devices as the THz source.