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

Abstract

Mesa structures made of Bi2Sr2CaCu2O8+δ high-temperature superconductor represent stacks of atomic scale intrinsic Josephson junctions. They can be used for generation of high-frequency electromagnetic waves. Here we analyze Josephson emission from small-but-high mesas (with a small area, but containing many stacked junctions). We have found strong evidence for tunable terahertz emission with a good efficacy in a record high-frequency span 1–11 THz, approaching the theoretical upper limit for this superconductor. Emission maxima correspond to in-phase cavity modes in the mesas, indicating coherent superradiant nature of the emission. We conclude that terahertz emission requires a threshold number of junctions N ~ 100. The threshold behavior is not present in the classical description of stacked Josephson junctions and suggests importance of laser-like cascade amplification of the photon number in the cavity.

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

“…For typical stacks with lateral sizes in the 100-μm range the emission frequency ranges from 0.2 to 2.4 THz [25][26][27]35]. Further, it has been shown recently that also smaller stacks can emit radiation between 1 and 11 THz [37].…”

Improved excitation mode selectivity of high-Tc superconducting terahertz emitters

“…12,39,54 Very recently, however, this record was greatly broken with a much thinner and narrower rectangular Bi2212 device that was cut to produce two emitters and detectors, and emissions covering the entire 1-11 THz range were observed. 13 Here, we show further progress obtained using our type of device structure. For most previous non-SAM rectangular devices, excitation of the TM 1,0 mode, consisting of a half wavelength centered across the width of the device, was commonly observed.…”

“…However, in 2007, the discoveries of strong, coherent, and continuous radiation obtained from one-dimensional stacks of intrinsic Josephson junctions (IJJs) in devices fabricated from single crystals of the high transition-temperature T c superconductor Bi 2 Sr 2 CaCu 2 O 8þd (Bi2212) have provided a competitive field of research in this entire THz frequency range. [8][9][10][11][12][13] In addition to spanning the entire frequency range from 0.3 to 11 THz, 12,13 these superconducting IJJ-THz emitters have been shown to exhibit additional advantages over those leading semiconducting devices with regard to the coherent nature of the THz electromagnetic wave emission.…”

“…The IJJ-THz emitters based upon superconducting Bi2212 single crystals have intensively been developed both experimentally and theoretically. [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] So far, the best performance has been achieved within the frequency range from 0.3 to 11 THz, [11][12][13]34,35,39 with the maximum output power of $30 lW, [31][32][33][34]39 and with a spectral width of the coherent and continuous emission of THz radiation that is generally less than 0.5 GHz, and under appropriate conditions, it was reported to be narrower than 23 MHz and possibly even 6 MHz. [23][24][25] Furthermore, a synchronized operation of an array of three such emitters was reported to yield the greatly enhanced power of 610 lW.…”

Optical Transistor for Amplification of Radiation in a Broadband Terahertz Domain

“…These devices produce radiation with Josephson oscillations generated by an applied bias voltage [12,13]. Here a tunable THz emission in a record wide frequency range, spanning from 1 to 11 THz, has been recently observed [14]. However, the power output is only up to 1 µW, which is still inadequate for practical applications.…”