1,030 research outputs found
Dispersion-Engineered Traveling Wave Kinetic Inductance Parametric Amplifier
A traveling wave kinetic inductance parametric amplifier comprises a superconducting transmission line and a dispersion control element. The transmission line can include periodic variations of its dimension along its length. The superconducting material can include a high normal state resistivity material. In some instances the high normal state resistivity material includes nitrogen and a metal selected from the group consisting of titanium, niobium and vanadium. The traveling wave kinetic inductance parametric amplifier is expected to exhibit a noise temperature below 100 mK/GHz
Noise Properties of Superconducting Coplanar Waveguide Microwave Resonators
We have measured noise in thin-film superconducting coplanar waveguide
resonators. This noise appears entirely as phase noise, equivalent to a jitter
of the resonance frequency. In contrast, amplitude fluctuations are not
observed at the sensitivity of our measurement. The ratio between the noise
power in the phase and amplitude directions is large, in excess of 30 dB. These
results have important implications for resonant readouts of various devices
such as detectors, amplifiers, and qubits. We suggest that the phase noise is
due to two-level systems in dielectric materials.Comment: 4 pages, 3 figures, accepted for publication in Applied Physics
Letter
Millimeter-Wave Lumped Element Superconducting Bandpass Filters for Multi-Color Imaging
The opacity due to water vapor in the Earth's atmosphere obscures portions of the sub-THz spectrum (mm/sub-mm wavelengths) to ground based astronomical observation. For maximum sensitivity, instruments operating at these wavelengths must be designed to have spectral responses that match the available windows in the atmospheric transmission that occur in between the strong water absorption lines. Traditionally, the spectral response of mm/sub-mm instruments has been set using optical, metal-mesh bandpass filters [1]. An alternative method for defining the passbands, available when using superconducting detectors coupled with planar antennas, is to use on-chip, superconducting filters [2]. This paper presents the design and testing of superconducting, lumped element, on-chip bandpass filters (BPFs), placed inline with the microstrip connecting the antenna and the detector, covering the frequency range from 209–416 GHz. Four filters were designed with pass bands 209–274 GHz, 265–315 GHz, 335–361 GHz and 397–416 GHz corresponding to the atmospheric transmission windows. Fourier transform spectroscopy was used to verify that the spectral response of the BPFs is well predicted by the computer simulations. Two-color operation of the pixels was demonstrated by connecting two detectors to a single broadband antenna through two BPFs. Scalability of the design to multiple (four) colors is discussed
Temperature dependence of the frequency and noise of superconducting coplanar waveguide resonators
We present measurements of the temperature and power dependence of the resonance frequency and frequency noise of superconducting niobium thin-film coplanar waveguide resonators carried out at temperatures well below the superconducting transition (Tc=9.2 K). The noise decreases by nearly two orders of magnitude as the temperature is increased from 120 to 1200 mK, while the variation of the resonance frequency with temperature over this range agrees well with the standard two-level system (TLS) model for amorphous dielectrics. These results support the hypothesis that TLSs are responsible for the noise in superconducting microresonators and have important implications for resonator applications such as qubits and photon detectors
A kinetic inductance detectors array design for high background conditions at 150 GHz
We present a design for an array of kinetic inductance detectors (KIDs)
integrated with phased array antennas for imaging at 150 GHz under high
background conditions. The microstrip geometry KID detectors are projected to
achieve photon noise limited sensitivity with larger than 100 pW absorbed
optical power. Both the microstrip KIDs and the antenna feed network make use
of a low-loss amorphous silicon dielectric. A new aspect of the antenna
implementation is the use of a NbTiN microstrip feed network to facilitate
impedance matching to the 50 Ohm antenna. The array has 256 pixels on a 6-inch
wafer and each pixel has two polarizations with two Al KIDs. The KIDs are
designed with a half wavelength microstrip transmission line with parallel
plate capacitors at the two ends. The resonance frequency range is 400 to 800
MHz. The readout feedline is also implemented in microstrip and has an
impedance transformer from 50 Ohm to 9 Ohm at its input and output.Comment: 6 pages, 3 figures, Journal of Low Temperature Physic
Electron-phonon coupling in Ti/TiN MKIDs multilayer microresonator
Over the last few years there has been a growing interest toward the use of
superconducting microwave microresonators operated in quasi-thermal equilibrium
mode, especially applied to single particle detection. Indeed, previous devices
designed and tested by our group with X-ray sources in the keV range evidenced
that several issues arise from the attempt of detection through athermal
quasiparticles produced within direct strikes of X-rays in the superconductor
material of the resonator. In order to prevent issues related to quasiparticles
self-recombination and to avoid exchange of athermal phonons with the
substrate, our group focused on the development of thermal superconducting
microresonators. In this configuration resonators composed of multilayer films
of Ti/TiN sense the temperature of an absorbing material. To maximize the
thermal response, low critical temperature films are preferable. By lowering
the critical temperature, though, the maximum probing power bearable by the
resonators decrease abruptly because of the weakening of the electron-phonon
coupling. A proper compromise has to be found in order to avoid signal to noise
ratio degradation. In this contribution we report the latest measurement of the
electron-phonon coupling
Measurement of loss in superconducting microstrip at millimeter-wave frequencies
We have developed a new technique for accurate measurement of the loss of superconducting microstrips at mm-wave frequencies. In this technique, we optically couple power to slot antenna, which is connected to one port of a hybrid coupler. One of the output ports of the hybrid delivers power to a series of mm-wave microstrip resonators which are capacitively coupled to a feedline followed by an MKID (microwave kinetic inductance detector) that measures the transmitted power. Two other MKIDs are connected to the remaining ports of the hybrid to measure the total incident optical power and the power reflected from the mm-wave resonators, allowing |S_(21)|^2 and |S_(11)|^2 to be accurately determined and resonance frequency fr and quality factor Q to be retrieved. We have fabricated such a Nb/SiO_2/Nb microstrip loss test device which contains several mm- wave resonators with f_r~100 GHz and measured it at 30 mK. All the resonators have shown internal quality factor Qi~500–2000, suggesting a loss tangent of ~5×10^(−4)−2×10^(−3) for the SiO_2 in use. For comparison, we have also fabricated a 5 GHz microstrip resonator on the same chip and measured it with a network analyzer. The loss tangent at 5 GHz derived from fitting the f_0 and Q data to the two-level system (TLS) model is 6×10^(−4), about the same as from the mm-wave measurement. This suggests that the loss at both microwave and mm-wave frequencies is probably dominated by the TLS in SiO_2. Our results are of direct interest to mm/submm direct detection applications which use microstrip transmission lines (such as antenna-coupled MKIDs and transition-edge sensors), and other applications (such as on-chip filters). Our measurement technique is applicable up to approximately 1 THz and can be used to investigate a range of dielectrics
Integrated Focal Plane Arrays for Millimeter-wave Astronomy
We are developing focal plane arrays of bolometric detectors for sub-millimeter and millimeter-wave astrophysics. We propose a flexible array architecture using arrays of slot antennae coupled via low-loss superconducting Nb transmission line to microstrip filters and antenna-coupled bolometers. By combining imaging and filtering functions with transmission line, we are able to realize unique structures such as a multi-band polarimeter and a planar, dispersive spectrometer. Micro-strip bolometers have significantly smaller active volume than
standard detectors with extended absorbers, and can realize higher sensitivity and speed of response. The integrated array has natural immunity to stray radiation or spectral leaks, and minimizes the suspended mass operating at 0.1 - 0.3 K. We also discuss future space-borne spectroscopy and polarimetry applications
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