Superconducting noise bolometer with microwave bias and readout for array applications

Abstract

We present a superconducting noise bolometer for terahertz radiation, which is suitable for large-format arrays. It is based on an antenna-coupled superconducting micro-bridge embedded in a high-quality factor superconducting resonator for a microwave bias and readout with frequency-division multiplexing in the GHz range. The micro-bridge is kept below its critical temperature and biased with a microwave current of slightly lower amplitude than the critical current of the microbridge. The response of the detector is the rate of superconducting fluctuations, which depends exponentially on the concentration of quasiparticles in the micro-bridge. Excess quasiparticles are generated by an incident THz signal. Since the quasiparticle lifetime increases exponentially at lower operation temperature, the noise equivalent power rapidly decreases. This approach allows for large arrays of noise bolometers operating above 1 K with sensitivity, limited by 300-K background noise. Moreover, the response of the bolometer always dominates the noise of the readout due to relatively large amplitude of the bias current. We performed a feasibility study on a proof-of-concept device with a 1.0 × 0.5 m 2 micro-bridge from a 9-nm thin Nb film on a sapphire substrate. Having a critical temperature of 5.8 K, it operates at 4.2 K and is biased at the frequency 5.6 GHz. For the quasioptical input at 0.65 THz, we measured the noise equivalent power 3×10-12 W/Hz, which is close to expectations for this particular device in the noise-response regime.The demand for sensitive large-format arrays of THz detectors today exists in different terrestrial applications, e.g. THz imaging for non-destructive testing or imaging spectroscopy for material research [1][2][3][4] . The array performance, limited only by the noise of the roomtemperature background radiation (noise equivalent power, NEP photon ≈10-15 W/Hz 1/2 ), is desired at a moderate operation temperature (T b >2 K), which is provided by low-cost and compact cryogenic coolers. Previously, THz imaging arrays with ~10 2 pixels were demonstrated 5,6 . They met the sensitivity requirements, but suffered from rapidly growing complexity of the readout with an increase of the array size. A remarkable example of an array-scalable sensor is the microwave kinetic inductance detector (MKID) 7 , which is based on high-Q superconducting resonators. Along with frequency-division multiplexing (FDM) in the GHz range, this approach allows for building kilo-pixel arrays using powerful software-defined radio (SDR) 8 . However, THzrange pair-braking MKIDs are using superconductors with small energy gap and operating at T b~1 00 mK, which requires expensive and bulky cryogenics. Another type of THz-range array-scalable detector, which is able to work at T b >2 K, is the kinetic inductance bolometer (KIBs) 9,10 . Each KIB is a lumped-element resonator on a suspended absorptive membrane. The NEP≈10 -14 W/Hz 1/2 was reported for the large array of KIBs 11 . However, due to relatively high AC losses, the resonator...

Superconducting bolometer with high-frequency readout circuit at 400 mK

“…The presence of active high-frequency losses at a temperature below the critical one is precisely the mechanism that makes it possible to realize the nonlinear impedance of microbridge with an electron gas. Note that high-frequency heating and critical current switching [10,13] seem to be competitive processes when RFTES enters the operating mode, which is interesting for further detailed study.…”

“…Analogy with the classical TES is appropriate here, the operating point of which is automatically set to the operating resistance after reaching the critical current and the subsequent " jump" to the resistive state. RFTES mode with critical current was analyzed in our works [10][11][12][13]. However, the calculation (Fig.…”

“…2, c). More detailed description of the design and manufacturing procedure of the chip can be found in the works [12,13].…”

“…Recently, there has been an upsurge in interest on the part of the astrophysical community in ultrasensitive imaging direct terahertz detectors based on superconducting materials, especially in the form of integrated arrays with a number of pixels of ∼ 1000 [1][2][3][4][5][6][7], including those on orbital carriers. The monolithic detector proposed by us, which received the abbreviation RFTES (radio frequency transition edge sensor) [8][9][10][11][12][13][14][15][16], is a nonequilibrium thermal detector and retains the features of known superconducting detectors, having several advantages. The response of the detector is based on the high-frequency nonlinearity of the surface impedance of a superconductor [17], formed as a thin-film microbridge, included in a high-Q quarterwave resonator.…”

Review of Broadband Metamaterial Absorbers: From Principles, Design Strategies, and Tunable Properties to Functional Applications

“…[ 598 ] In electronics, it measures the output power of microwave sources. [ 599 ] All of these require a radiometer to ensure the smooth operation; thus, the combination of broadband, high absorption, polarization insensitive, wide‐angle tolerance, and other excellent characteristics of BMAs could maximize the application potentials. [ 538–546 ]…”