Hilbert spectroscopy from gigahertz to terahertz frequencies by high-Tc Josephson junctions (original) (raw)
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IEEE Transactions on Appiled Superconductivity, 1999
First laboratory prototypes of Hilbert-transform spectrometers have been developed. To meet the requirements of Hilbert-transform spectroscopy, high-T c Josephson junctions with RSJ-like behavior have been fabricated on twin-free NdGaO 3 bicrystal substrates. The operation of the spectrometers has been demonstrated from 60 GHz up to 2.25 THz. The first out-of-lab application of Hilbert-transform spectrometers has been successfully demonstrated at the TESLA Test Facility linear accelerator at DESY (Hamburg). The spectra of coherent transition electromagnetic radiation from electron bunches have been measured and a bunch length of s t = 1.2 ps has been derived from these spectra. The market perspectives of Hilbert spectrometers have been estimated.
Terahertz Hilbert-transform spectral analysis with high-Tc Josephson junctions: first applications
1998
Our recent results on Hilbert-transform spectral analysis based on ac Josephson effect are reported. High-quality epitaxial YBa2Cu3O7-x thin-film Josephson junctions have been fabricated on untwinned (110) NdGaO3 bicrystal substrates to satisfy the operational requirements of Hilbert-transform technique. The design and characteristics of the developed laboratory Hilbert-transform spectrometers are presented. Spectra of Josephson radiation in high-Tc junctions have been measured in the frequency range from 60 to 2250 GHz, and a Lorentzian shape of Josephson radiation has been obtained both for equilibrium (eV very much less than kT) and nonequilibrium (eV very much greater than kT) cases. The first spectral measurements of coherent transition radiation at Test Facility Linear Accelerator at the Deutsches Elektronen-Synchrotron DESY (Hamburg) have been made and the length of electron bunches of 1.2 ps has been determined from these spectra. The comparison of Hilbert-transform spectral analysis with conventional techniques is presented.
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.
Far-infrared broadband measurements with Hilbert spectroscopy
Physica C: Superconductivity, 2002
A principal possibility of broadband far-infrared (FIR) spectral measurements with Hilbert-transform technique, based on ac Josephson effect, has been experimentally studied. High-pressure 200W mercury arc lamp was used as a source of FIR broadband radiation. The grain-boundary YBaCuO thin-film Josephson junctions (JJ) with the normal-state resistance Rn=1-3 Ohm and the IcRn-product up to 1 mV were used in the experiments. Broadband spectra with different far-infrared mesh-type filters have been measured by this technique. First results on the detection of gas absorption spectra in FIR range with Hilbert spectroscopy (HS) were obtained. Several lines of CO absorption spectrum in the range from 300 up to 1000 GHz have been resolved, when broadband blackbody radiation passed through a gas cell.
Journal of Physics: Conference Series, 2006
Detection of terahertz radiation using YBa 2 Cu 3 O 7-x [100]-tilt bicrystal junctions with high I c R n -product up to 6 mV has been studied. Two types of the responses ΔV (V) have been observed. At low frequencies up to some frequency f l , the responses ΔV (V) were proportional to the second derivative of the V(I)-curve. At high frequencies f > f l , the responses ΔV (V) demonstrate odd-symmetric resonances at V = hf/2e. For low-resistance junctions, Josephson frequency-selective detection was found up to the frequency of 5.3 THz, which is above the frequency of the strongest optical mode (f 0 = 4.6 THz) in YBa 2 Cu 3 O 7-x . The frequency f l was found to increase with the resistance R n and the I c R n -product of the junction. For high-resistance junctions with R n = 23 Ω, classical detection was observed up to 0.4 THz range. The difference in detection mechanisms is attributed to a continuous type of spectra of Josephson oscillations at low voltages and to a discrete type of Josephson spectra at high voltages. Computer simulation of a Josephson detector has been carried out, considering intensive thermal fluctuations and a frequency-dependent impedance of the Josephson junction. It is shown that a classical detector, based on the [100]-tilt Josephson junctions with R n =100 Ohm at T = 40 K, might reach the values of noise equivalent power NEP <2⋅ 10 -14 W/Hz 1/2 at the frequencies up to 1.8 THz.
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.
Applied Sciences
Spectral analysis of terahertz (THz) and sub-THz emission from quantum cascade lasers has been recently demonstrated using conventional YBa2Cu3O7−x bicrystal Josephson junctions made from c-axes thin films. Josephson frequencies of alternative bicrystal junctions made from YBa2Cu3O7−x films with mutually tilted c-axes extend further into the THz range. However, these THz oscillations can weaken due to new absorption channels in the junction environment. Here, using Josephson admittance spectroscopy, THz losses in YBa2Cu3O7−x bicrystal junctions with mutually tilted c-axes are studied. Absorption maximizes at a reproducible set of THz frequencies close to those of collective modes in bulk YBa2Cu3O7−x recovered by Fourier spectroscopy. Annealing junctions in atomic oxygen reduces the losses at frequencies of 2.7 and 3.6 THz, while the losses increase at frequencies of 2.3 and 4.6 THz. Thus, as a THz spectrum analyzer, YBa2Cu3O7−x bicrystal junctions require post-fabrication correction...
IEEE Transactions on Appiled Superconductivity, 1997
We have demonstrated the first applications of Josephson-effect-based Hilbert-transform spectral analysis using high-Tc Josephson junctions. Y B a~C u 3 0 7 -~ grainboundary Josephson junctions have been fabricated on (110) NdGa03 bicrystal substrates for these measurements. At first, spectra of Josephson radiation have been measured by Hilberttransform technique in the range 60 -800 GI%. A Lorentzian shape oft Josephson radiation and possibility to obtain a spectral resolution as low as 0.1 cm-1 in the submillimeterwave range has been demonstrated at liquid nitrogen temperature. At second, spectra of high-harmonic content of the radiation coming from commercial millimeter-wave oscillators have been measured by Hilbert-transform technique in the spectral range from 60 to 450 GHz. The comparison o f Hilbert-transform spectral analysis with conventional techniques is given.
Terahertz spectroscopy by Josephson oscillator and cold-electron bolometer
2004
For sensitive wideband spectroscopy at THz frequencies with performance better than for Fourier Transform Spectrometer, one needs a wide-range electrically tunable, narrow linewidth THz source, and a sensitive broadband detector. To obtain a low noise level of sensor we use a superconducting normal metal cold electron bolometer (CEB). A voltage response of the bolometer is 4 . 10 8 V/W and an amplifier-limited technical noise equivalent power of the bolometer is 1.25 . 10 -17 W/Hz 1/2 . The wide band electrically tuned terahertz band cryogenic oscillator is a Josephson junction. Contrary to conventional Josephson junctions based on niobium, and naturally limited in frequency by energy gap of about 700 GHz, the high critical temperature YBaCuO junctions can extend this limit by an order of magnitude. At 4 K such oscillators can radiate at frequencies exceeding 2 THz. Signals received by bolometers integrated with double-dipole and log-periodic antennas and irradiated by the Josephson oscillator show in our experiments the high frequency response corresponding to an oscillation frequency of up to 1.75 THz. Such cryogenic terahertz network analyzer is suitable for low-signal spectral evaluation of cryogenic detectors, quasioptical sub-mm cryogenic filters, planar antennas with planar microwave filters, integrated structures comprising such elements, and arrays of cryogenic receivers.