Aims. Future astrophysics and cosmic microwave background space missions operating in the far-infrared to millimetre part of the spectrum will require very large arrays of ultra-sensitive detectors in combination with high multiplexing factors and efficient lownoise and low-power readout systems. We have developed a demonstrator system suitable for such applications. Methods. The system combines a 961 pixel imaging array based upon Microwave Kinetic Inductance Detectors (MKIDs) with a readout system capable of reading out all pixels simultaneously with only one readout cable pair and a single cryogenic amplifier. We evaluate, in a representative environment, the system performance in terms of sensitivity, dynamic range, optical efficiency, cosmic ray rejection, pixel-pixel crosstalk and overall yield at an observation centre frequency of 850 GHz and 20% fractional bandwidth. Results. The overall system has an excellent sensitivity, with an average detector sensitivity NEP det = 3 × 10 −19 W/ √ Hz measured using a thermal calibration source. At a loading power per pixel of 50 fW we demonstrate white, photon noise limited detector noise down to 300 mHz. The dynamic range would allow the detection of ∼1 Jy bright sources within the field of view without tuning the readout of the detectors. The expected dead time due to cosmic ray interactions, when operated in an L2 or a similar far-Earth orbit, is found to be <4%. Additionally, the achieved pixel yield is 83% and the crosstalk between the pixels is <−30 dB. Conclusions. This demonstrates that MKID technology can provide multiplexing ratios on the order of a 1000 with state-of-the-art single pixel performance, and that the technology is now mature enough to be considered for future space based observatories and experiments.

The Néel IRAM KIDs Array (NIKA) is a fully integrated measurement system based on kinetic inductance detectors (KIDs) currently being developed for millimeter wave astronomy. The instrument includes dual-band optics allowing simultaneous imaging at 150 GHz and 220 GHz. The imaging sensors consist of two spatially separated arrays of KIDs. The first array, mounted on the 150 GHz branch, is composed of 144 lumped-element KIDs. The second array (220 GHz) consists of 256 antenna-coupled KIDs. Each of the arrays is sensitive to a single polarization; the band splitting is achieved by using a grid polarizer. The optics and sensors are mounted in a custom dilution cryostat, with an operating temperature of ∼70 mK. Electronic readout is realized using frequency multiplexing and a transmission line geometry consisting of a coaxial cable connected in series with the sensor array and a lownoise 4 K amplifier. The dual-band NIKA was successfully tested in 2010 October at the Institute for Millimetric Radio Astronomy (IRAM) 30 m telescope at Pico Veleta, Spain, performing in-line with laboratory predictions. An optical NEP was then calculated to be around 2 × 10 −16 W Hz −1/2 (at 1 Hz) while under a background loading of approximately 4 pW pixel −1 . This improvement in comparison with a preliminary run (2009) verifies that NIKA is approaching the target sensitivity for photon-noise limited ground-based detectors. Taking advantage of the larger arrays and increased sensitivity, a number of scientifically relevant faint and extended objects were then imaged including the Galactic Center SgrB2 (FIR1), the radio galaxy Cygnus A, and the NGC1068 Seyfert galaxy. These targets were all observed simultaneously in the 150 GHz and 220 GHz atmospheric windows.

We demonstrate photon noise limited performance in both phase and amplitude readout in microwave kinetic inductance detectors (MKIDs) consisting of NbTiN and Al, down to 100 fW of optical power. We simulate the far field beam pattern of the lens-antenna system used to couple radiation into the MKID and derive an aperture efficiency of 75%. This is close to the theoretical maximum of 80% for a single-moded detector. The beam patterns are verified by a detailed analysis of the optical coupling within our measurement setup. V C 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4829657]In the next decades millimeter and sub-mm astronomy require 1 large format imaging arrays to complement the high spatial resolution of the Atacama Large Millimeter/ submillimeter Array.2 The desired sensors should have a background limited sensitivity and a high optical efficiency and enable arrays of up to megapixels in size. The most promising candidates to fulfill these requirements are microwave kinetic inductance detectors (MKIDs) 3 due to their inherent potential for frequency domain multiplexing. MKIDs are superconducting resonators, thousands of which can be coupled to a single feedline. Each resonator is sensitive to changes in the Cooper pair density induced by absorption of sub-mm radiation. By monitoring the change in either phase or amplitude of the complex feedline transmission at the MKID resonance one can measure the absorbed photon power. Using amplitude readout photon noise limited performance has been shown. 4 However, for practical applications two key properties need to be demonstrated: (1) Photon noise limited operation in phase readout. (2) A measurement of the aperture efficiency, 5 which describes the absolute optical coupling of a MKID imaging array to a plane wave.In this letter we present antenna coupled hybrid NbTiNAl MKIDs designed for groundbased sub-mm astronomy. We show that these devices achieve photon noise limited performance in both amplitude and phase readout. Through a detailed analysis of the optical coupling within our setup we validate the simulation of the lens-antenna far field beam pattern. From this we derive an aperture efficiency of 75%. This is close to the theoretical maximum of 80% for a single-moded detector.The device design, shown in Fig. 1, aims to simultaneously maximize the phase response and minimize the two-level system (TLS) noise contribution. 8 The device is a L % 5 mm long quarter wavelength coplanar waveguide (CPW) resonator consisting of two sections. The first section ($4 mm), at the open end of the resonator, is a wide CPW made entirely from 200 nm thick NbTiN. NbTiN has 10 dB lower TLS noise than conventional superconductors such as Al. 9 The TLS noise is further reduced by the width of the CPW, 9 23.7 lm and 5.4 lm for the CPW gap and central line, respectively.The second section (1 mm), at the shorted end of the resonator, is a narrow CPW with NbTiN groundplanes and a 48 nm thick Al central line. The Al is galvanically connected to the NbTiN central line (Fig. 1...

Microwave Kinetic Inductance Detectors (MKIDs) have shown great potential for sub-mm instrumentation because of the high scalability of the technology. Here we demonstrate for the first time in the sub-mm band (0.1. . . 2 mm) a photon noise limited performance of a small antenna coupled MKID detector array and we describe the relation between photon noise and MKID intrinsic generation-recombination noise. Additionally we use the observed photon noise to measure the optical efficiency of detectors to be 0.8 ± 0.2. PACS numbers: 07.57.Kp Advances in sub-mm astronomy (100. . . 1000 GHz) have always been driven by advances in radiation detection technology. Current state of the art imaging arrays consist of up to 1000 pixels of cryogenic detectors with a sensitivity approaching the photon noise limit 1 . Significant further advances in observing speed are only possible by increasing the pixel number. Microwave Kinetic Inductance detectors (MKIDs) 2 are very promising to use for very large arrays due to their intrinsic multiplexing capability 3 . Despite the very low reported values 4,5 of the (dark) Noise Equivalent Power (NEP) ∼ 3 × 10 −19 W/Hz 1/2 , MKIDs have yet to demonstrate photon noise limited performance. In this letter we demonstrate photon noise limited performance of a lens-antenna coupled MKID array. The presented device geometry ensures that all radiation to the antenna is converted into quasiparticles in the sensitive part of the MKID, which is made of Al. This design, combined with the recent observation of generation-recombination noise in an Al MKID 5 , enables the demonstration of photon noise limited radiation detection.The fundamental limit of any ideal photon integrating sub-mm detector is the noise associated with the Bose-Einstein fluctuations in photon arrival rate 6 which results in a photon noise limited NEP:where P is the sky power loading the detector at a frequency F from the sub-mm source. B is the photon occupation number per mode and m the efficiency from emission to detection of one mode. The (1 + mB) term is the correction to Poisson statistics due to wave bunching 6 . In the presented experiment m is small to enable low power coupling. a)MKIDs are superconducting pair breaking detectors, in which incident sky radiation changes the equilibrium between Cooper pairs and quasiparticles and hence the microwave conductivity in a planar superconducting resonator 2 . The number fluctuations between quasiparticles and Cooper pairs in the MKID will limit the device sensitivity giving a generation-recombination (g-r) NEP 5,7 :In the limit where the quasiparticle number in the MKID is dominated by the sky power then NEP G−R can be approximated by:where we only consider recombination noise contributions as quasiparticle creation is correlated with the photon arrival. Here N qp is the number of quasiparticles, τ is the quasiparticle recombination lifetime, η pb ∼ 0.6 is the efficiency for conversion of energy into quasiparticles 8 and ∆ is the superconducting gap. Under illumination we therefore...

Next generation sub-mm imaging instruments require kilo-pixel focal plane arrays filled with background limited detectors. Microwave kinetic inductance detectors (MKIDs) are a state-of-the-art detector for future instruments due to their inherent multiplexing capabilities. An MKID consists of a superconducting resonator coupled to a feed-line that is used for readout. In the device presented here radiation coupling is achieved by coupling the MKID directly to a planar antenna. The antenna is placed in the focus of an extended hemispherical lens to increase the filling factor and to match efficiently to fore optics. In this paper, we present the design and the optical performance of MKIDs optimized for operation in a 100-GHz band around 850 GHz. We have measured the coupling efficiency, frequency response, and beam patterns and compare those results to simulated performance. We obtain an excellent agreement between the measured and simulated beam pattern, frequency response, and absolute coupling efficiency between a thermal calibration source and the power absorbed in the detector. Additionally, we demonstrate that antenna coupled MKIDs offer background limited radiation detection down to ∼100 aW of power absorbed in the detector.