Terahertz Josephson spectral analysis and its applications

Abstract

Principles of Hilbert-transform spectral analysis (HTSA) are presented and advantages of the technique in the terahertz (THz) frequency range are discussed. THz HTSA requires Josephson junctions with high values of characteristic voltages IcRn and dynamics described by a simple resistively shunted junction (RSJ) model. To meet these requirements, [001]- and [100]-tilt YBa2Cu3O7−x bicrystal junctions with deviations from the RSJ model less than 1% have been developed. Demonstrators of Hilbert-transform spectrum analyzers with various cryogenic environments, including integration into Stirling coolers, are described. Spectrum analyzers have been characterized in the spectral range from 50 GHz to 3 THz. Inside a power dynamic range of five orders, an instrumental function of the analyzers has been found to have a Lorentz form around a single frequency of 1.48 THz with a spectral resolution as low as 0.9 GHz. Spectra of THz radiation from optically pumped gas lasers and semiconductor frequency multipliers have been studied with these spectrum analyzers and the regimes of these radiation sources were optimized for a single-frequency operation. Future applications of HTSA will be related with quick and precise spectral characterization of new radiation sources and identification of substances in the THz frequency range.

Nonmonotonous temperature dependence of Shapiro steps in YBCO grain boundary junctions

“…For applied tasks of terahertz imaging [ 47 ], mixing [ 36 ], and Hilbert-transform spectral analysis [ 13 ] it is not possible to vary the incident power over a wide range. The power level is set there by losses, mismatch, and power absorption by the samples under study.…”

“…Josephson junctions have also been used for various spectroscopic applications [ 12 ]. In this area, the AC Josephson effect is utilized for the Hilbert-transform spectral analysis [ 13 – 14 ].…”

Highly-Conformal Sputtered Through-Silicon Vias With Sharp Superconducting Transition

“…We also believe that some minor modifications in TSV design and implementation, such as a relaxation of the geometrical transition from the wafer surface to the funnel and sputtering of other types of materials, could suffice to enable applications in support of e.g. photodetectors and other superconducting astronomical instruments exploiting the THz range of the electromagnetic spectrum [25], [26].…”

HTS Josephson junctions arrays for high-frequency mixing

“…The main steps are illustrated in Figure 1 (a-f), and an optical picture of a N=8 JJA with a spacing S=80 nm is presented in Figure 1 (g). In short, we start from a commercial 70 nm thick YBa 2 Cu 3 O 7 film grown on a sapphire substrate 2 , and covered with a 250 nm gold layer. The spiral antenna and the CPW transmission line are first defined in the gold layer through a ma-N e-beam patterned resist 3 , followed by a 500-eV Ar + Ion Beam Etching.…”

“…While High Temperature Superconductors (HTSc) have been identified as promising materials to make high frequency (THz) Josephson devices for a long time, recent spectacular developments in the field are making this happening for real [1][2][3]. The era of THz devices based on HTSc Josephson Junctions (JJ) is opening, and one can explore the potentialities of different techniques able to produce them.…”