Terahertz and Millimetre Wave Imaging with a Broadband Josephson Detector Working above 77 K (original) (raw)

Terahertz imaging using a high- T c superconducting Josephson junction detector

Superconductor Science and Technology, 2008

A high-T c superconducting (HTS) detector based on a YBa 2 Cu 3 O 7−x (YBCO) step-edge Josephson junction has been developed and applied to terahertz (THz) detection. The detector was coupled to a ring-slot antenna designed for operation at 600 GHz, and used for THz imaging. The results suggest that the characteristic voltage and frequency of our HTS step-edge junctions can be readily optimized for the chosen THz frequency range at easily achievable temperatures. The images also clearly demonstrate some of the unique properties of THz radiation, including the sensitivity to water content and the ability to penetrate packaging materials.

Detection of Pulsed Terahertz Waves Using High-Temperature Superconductor Josephson Junction

Applied Physics Express, 2010

We report a novel terahertz (THz) detector with a high-T c superconducting (HTS) Josephson junction. This detector was fabricated using a YBa 2 Cu 3 O 7À grain boundary junction. Clear THz signals induced by THz-pulse radiation from an ultrafast photoconductive antenna excited by femtosecond optical pulses were observed. We investigated the characteristics of the detector by changing the parameters of THz radiation such as pump laser power for the THz emitter and THz polarization. The results indicate that the detector mainly detects the THz electric fields. This is the first demonstration of a detection of pulsed THz electric fields using an HTS Josephson junction.

THz Radiation Measurement with HTSC Josephson Junction Detector Matched to Planar Antenna

Applied Sciences, 2020

Superconducting Josephson junctions have major advantages as detectors of millimeter wave radiation. Frequency of the radiation can be easily derived from the Shapiro steps of the current-voltage characteristics. However, system performance is highly sensitive to impedance mismatch between the antenna and the junction; therefore, optimization is essential. We analyzed and implemented an improved antenna structure, in which the junction is displaced from the antenna center and placed between the ends of two matching strips. Based on theoretical analysis and advanced electromagnetic simulations, we optimized strip dimensions, which affect both the detection magnitude and the frequency of the reflection coefficient dip. Accordingly, two Au bow-tie antennas with different matching strip widths were fabricated. Superconducting Yttrium Barium Copper Oxide (YBCO) thin films were deposited exactly at the bicrystal substrate misorientation points, forming Josephson junctions at the ends of t...

Toward terahertz heterodyne detection with superconducting Josephson junctions

Applied Physics Letters, 2012

In this letter, we present the study of the high-frequency mixing properties of ion irradiated YBa2Cu3O7 Josephson nano-junctions. The frequency range, spanning above and below the characteristic frequencies fc of the junctions, permits a clear observation of the transition between two mixing regimes. The experimental conversion gain was found to be in good agreement with the prediction of the three ports model. Finally, we discuss the potential of the junctions to build a Josephson mixer operating in the terahertz frequency range.

High-Tc superconducting Josephson mixers for terahertz heterodyne detection

Journal of Applied Physics, 2014

We report on an experimental and theoretical study of the high-frequency mixing properties of ion-irradiated YBa2Cu3O7 Josephson junctions embedded in THz antennas. We investigated the influence of the local oscillator power and frequency on the device performances. The experimental data are compared with theoretical predictions of the general three-port model for mixers in which the junction is described by the resistively shunted junction model. A good agreement is obtained for the conversion efficiency in different frequency ranges, spanning above and below the characteristic frequencies fc of the junctions.

Terahertz Detection and Spectroscopy Based on High-Tc Josephson Junctions

2005 18th International Conference on Applied Electromagnetics and Communications, 2005

Frequency-selective and broadband high-T c Josephson detectors have been fabricated and characterized. A spectral range from 15 GHz to 5.3 THz has been demonstrated for these detectors. A power dynamic range of 50 dB and a noise equivalent power of 10 -14 W/Hz 1/2 have been realized. A spectral resolution δf/f of 10 -3 has been achieved in the terahertz range. As an alternative to Fourier-transform spectroscopy, fast Hilbert-transform spectroscopy, based on these detectors, has been applied for various cw and pulsed terahertz sources.

Frequency detection of focused sub-THz waves using a high-Tc Josephson junction

Physica C: Superconductivity, 2005

We have proposed a new type of frequency detection system of sub-terahertz electromagnetic waves using a photomixing technique and a Josephson junction detector. The photomixer illuminated by two lasers with different wavelengths generates coherent electromagnetic waves that include a frequency component corresponding to the frequency difference of the two lasers. The generated electromagnetic waves were radiated from a horn antenna and focused to the Josephson junction detector with Si lens. The high-T c Josephson junction operates as a frequency detector for electromagnetic waves. Using this system, we observed the Shapiro steps of 188 lV that correspond to the frequencies of 90.8 GHz.

Signal and Noise Characteristics of Terahertz Frequency-Selective and Broadband High-$T_{c}$ Josephson Detectors

IEEE Transactions on Applied Superconductivity, 2000

Josephson detectors based on YBa 2 Cu 3 O 7-x [100]-tilt bicrystal junctions were fabricated and their frequency-selective and broadband modes of operation were studied at terahertz frequencies. The resistances of the [100]-tilt junctions were in the range of 1-200 Ohm and their characteristic voltages were up to 8 mV at 4.2 K. Values of the responsivity up to 7·10 4 V/W at radiation frequency of 0.7 THz were demonstrated for the low-resistance frequency-selective detectors at a temperature of 55 K. The responsivity values were found to be in accordance with the predictions of the RSJ model, when only thermal fluctuations are considered. But, the values of noise equivalent power (NEP) and power dynamic range measured in the same experiment at a modulation frequency of 2 kHz were found to be determined by 1/f noise of the junctions and equal to 3·10 -13 W/Hz 1/2 and 5·10 4 , correspondingly. It was shown that the values of NEP of 5·10 -15 W/Hz 1/2 and power dynamic range of 10 6 could be reached in this mode if high-frequency modulation or pulsed radiation were used. Broadband classical detection in high-resistance [100]-tilt junctions was experimentally found to reach the terahertz range. It follows from numerical simulations that broadband detection by the [100]-tilt YBCO junction with the resistance of 300 Ohm might be characterized by NEP-values down to 3·10 -15 W/Hz 1/2 and a bandwidth of 1.5 THz. Josephson detectors based on YBCO [100]-tilt bicrystal junction are promising for various terahertz applications such as real-time spectral analysis of continuous or pulsed radiation sources and terahertz imaging for medical or security screening.

High sensitivity high Tc superconducting Josephson junction antenna for 200 GHz detection

Journal of Electromagnetic Waves and Applications, 2018

A high sensitivity rounded bow-tie antenna was optimized based on electromagnetic simulations. The bicrystal Josephson junction detector with a thin layer of YBCO was located exactly at the bicrystal misorientation point at the center of the antenna. The Au antenna was fabricated on an (100) MgO bicrystal substrate. In the presence of 200 GHz RF radiation, a noise equivalent power (NEP) of around 6×10 −12 W Hz −1/2 was measured, with a voltage sensitivity, η(V), of 30 dB with the detector at 60 K. Even though no coupling lens was used, these results are as good as those reported in systems in which the impinging radiation was focused with lenses over the detectors. Thus, important simplification of the system was obtained without loss of sensitivity.

Millimeter-wave Hilbert-transform spectroscopy with high-Tc Josephson junctions

Applied Physics Letters, 1996

The application of Hilbert-transform spectroscopy for the measurement of high-harmonic content of the radiation from a frequency multiplier has been demonstrated in the spectral range from 60 to 450 GHz. YBa 2 Cu 3 O 7-x grain-boundary Josephson junctions made on (110) NdGaO 3 bicrystal substrates have been used in these experiments. The internal Josephson radiation of the junctions reveals a Lorentzian shape due to thermal noise broadening. The possibility to obtain a spectral resolution as low as 280 MHz (0.01 cm -1 ) has been shown with a Josephson junction operating at liquid nitrogen temperature.