Ultra Low Background Cryogenic Test Facility for Far-Infrared Radiation Detectors

Baselmans, J. J. A.; Yates, S. J. C.; Diener, P.; Visser, Pieter de

doi:10.1007/s10909-012-0511-0

Cited by 34 publications

(34 citation statements)

References 12 publications

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“…The samples are cooled in a pulse tube pre-cooled adiabatic demagnetization refrigerator. Special care has been taken to make the setup light tight [4,9], presented in detail in an accompanying paper [10]. The complex transmission of the microwave circuit is measured with a quadrature mixer and traces out a circle in the complex plane [1,11].…”

Section: Microwave Resonator Experimentsmentioning

confidence: 99%

Generation-Recombination Noise: The Fundamental Sensitivity Limit for Kinetic Inductance Detectors

et al. 2012

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We present measurements of quasiparticle generation-recombination noise in aluminium Microwave Kinetic Inductance Detectors, the fundamental noise source for these detectors. Both the quasiparticle lifetime and the number of quasiparticles can be determined from the noise spectra. The number of quasiparticles saturates to 10 µm −3 at temperatures below 160 mK, which is shown to limit the quasiparticle lifetime to 4 ms. These numbers lead to a generation-recombination noise limited noise equivalent power (NEP) of 1.5 × 10 −19 W/Hz 1/2 . Since NEP ∝ N qp , lowering the number of remnant quasiparticles will be crucial to improve the sensitivity of these detectors. We show that the readout power now limits the number of quasiparticles and thereby the sensitivity.

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Section: Microwave Resonator Experimentsmentioning

confidence: 99%

Generation-Recombination Noise: The Fundamental Sensitivity Limit for Kinetic Inductance Detectors

et al. 2012

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“…Care was taken to make the sample stage light-tight as described in Ref. [19], which is crucial to eliminating excess quasiparticles due to stray light. The complex transmission S 21 of the microwave circuit was measured with a vector network analyzer.…”

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confidence: 99%

Evidence of a Nonequilibrium Distribution of Quasiparticles in the Microwave Response of a Superconducting Aluminum Resonator

et al. 2014

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In a superconductor, absorption of photons with an energy below the superconducting gap leads to redistribution of quasiparticles over energy and thus induces a strong nonequilibrium quasiparticle energy distribution. We have measured the electrodynamic response, quality factor, and resonant frequency of a superconducting aluminium microwave resonator as a function of microwave power and temperature. Below 200 mK, both the quality factor and resonant frequency decrease with increasing microwave power, consistent with the creation of excess quasiparticles due to microwave absorption. Counterintuitively, above 200 mK, the quality factor and resonant frequency increase with increasing power. We demonstrate that the effect can only be understood by a nonthermal quasiparticle distribution. DOI: 10.1103/PhysRevLett.112.047004 PACS numbers: 74.25.nn, 07.57.Kp, 74.40.Gh, 74.78.-w A superconductor can be characterized by the density of states, which exhibits an energy gap due to Cooper pair formation, and the distribution function of the electrons, which in thermal equilibrium is the Fermi-Dirac distribution. When a superconductor is driven by an electromagnetic field, nonlinear effects in the electrodynamic response can occur, which are usually assumed to be due to a change in the density of states, the so-called pair-breaking mechanism [1]. These nonlinear effects can be described along the lines of a current dependent superfluid density n s ðT; jÞ ∝ n s ðTÞ½1 − ðj=j c Þ 2 , where j is the actual current density, j c the critical current density, and T the temperature. Observations such as the nonlinear Meissner effect [2] and nonlinear microwave conductivity [3,4] can be explained by a broadening of the density of states and a decreased n s . The quasiparticles are assumed to be in thermal equilibrium and a Fermi-Dirac distribution fðEÞ ¼ 1=½expðE=k B TÞ þ 1 is assumed, with E the quasiparticle energy and k B Boltzmann's constant.Here we demonstrate that a microwave field also has a strong effect on fðEÞ in the superconductor, and induces a nonlinear response. We present measurements of the electrodynamic response, quality factor, and resonant frequency of an Al superconducting resonator (at 5.3 GHz) as a function of temperature and microwave power at low temperatures T c =18 < T < T c =3. The response measurements, complemented with quasiparticle recombination time measurements, are explained consistently by a model based on a microwave-induced nonequilibrium fðEÞ. Redistribution of quasiparticles [5,6] due to microwave absorption [7] has been shown earlier to cause enhancement of the critical current [8], the critical temperature (T c ), and the energy gap [9]. These enhancement effects are most pronounced close to T c and were observed for temperatures T > 0.8T c . A representation of gap suppression and gap enhancement is shown in the inset to Fig. 1(b) [8]. The consequences of the redistribution of quasiparticles for the electrodynamic response were only studied theoretically for T > 0.5T c [10]. Redistributi...

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“…The sample is mounted in a sample holder inside a light-tight box, in a box-in-a-box configuration [20]. The 350 GHz radiation illuminating the KIDs is coming from a cryogenic black The KIDs are mounted in a sample box thermally anchored to the base temperature plate of the ADR (∼ 100 mK).…”

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confidence: 99%

Anomalous response of superconducting titanium nitride resonators to terahertz radiation

Bueno

Coumou

Zheng

et al. 2014

Applied Physics Letters

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We present an experimental study of KIDs fabricated of atomic layer deposited TiN films, and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with increasing radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride / aluminium (NbTiN/Al) and all-aluminium (allAl) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power (NEP) improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations. Superconducting resonators have been proposed as kinetic inductance detectors (KIDs) for sensitive multipixel radiation detection [1]. Antenna-coupled hybrid niobium titanium nitride / aluminium (NbTiN/Al) KIDs [2,3] and all-aluminium (all-Al) [4] have shown generationrecombination noise and photon noise limited performance. KIDs can also be constructed as lumped element kinetic inductance detectors (LEKIDs) [5] in which the KID is arranged as a photon absorbing area matched to free space. Aluminium LEKIDs have also shown generation-recombination and photon noise limited performance [6]. However, the low normal-state resistivity of Al makes the design of the absorber for very high frequency radiation complex. Therefore, superconductors with a high normal state resistivity have recently become of particular interest [9].A figure of merit F to optimize the responsivity of KIDs is defined as, with α sc the kinetic inductance fraction, τ the quasiparticle recombination time, Q i the internal quality factor, F res the resonance frequency, N (0) is the single spin electron density of states at the Fermi level, and V the volume of the KID. For example, Al KIDs have a long quasiparticle recombination time (a few milliseconds) and high internal quality factors (above one million), but their kinetic inductance fraction is low and their volume large.Superconducting materials with a high resistivity in the normal-state are promising because of their high quality factor and a long enough relaxation time. The high normal resistance implies a large sheet inductance, resulting in a large kinetic inductance fraction, which lowers the KID volume. The high surface impedance also eases matching to free space and optimises the photon absorption. Given the high quality NbTiN resonators pioneered by Barends et al. [7,8], titanium nitride (TiN) has been proposed, because it has the previously mentioned properties in addition to a tuneable critical temperature, which facilitates a relatively long quasiparticle lifetime [9]. Currently, several groups are studying the implementation of TiN KID devices and instruments [10][11][12][13][14]. However, a material like TiN has also drawn the attention of the condensed matter physics community, interested in the disorder-induced superconductorto-insulator transitio...

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Ultra Low Background Cryogenic Test Facility for Far-Infrared Radiation Detectors

Cited by 34 publications

References 12 publications

Generation-Recombination Noise: The Fundamental Sensitivity Limit for Kinetic Inductance Detectors

Generation-Recombination Noise: The Fundamental Sensitivity Limit for Kinetic Inductance Detectors

Evidence of a Nonequilibrium Distribution of Quasiparticles in the Microwave Response of a Superconducting Aluminum Resonator

Anomalous response of superconducting titanium nitride resonators to terahertz radiation

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