Multiplexed readout of kinetic inductance bolometer arrays

Kinetic inductance bolometer (KIB) technology is a candidate for passive sub-millimeter wave and terahertz imaging systems. Its benefits include scalability into large 2D arrays and operation with intermediate cryogenics in the temperature range of 5 -- 10 K. We have previously demonstrated the scalability in terms of device fabrication, optics integration, and cryogenics. In this article, we address the last missing ingredient, the readout. The concept, serial addressed frequency excitation (SAFE), is an alternative to full frequency-division multiplexing at microwave frequencies conventionally used to read out kinetic inductance detectors. We introduce the concept, and analyze the criteria of the multiplexed readout avoiding the degradation of the signal-to-noise ratio in the presence of a thermal anti-alias filter inherent to thermal detectors. We present a practical scalable realization of a readout system integrated into a prototype imager with 8712 detectors. This is used for demonstrating the noise properties of the readout. Furthermore, we present practical detection experiments with a stand-off laboratory-scale imager.Comment: 7 pages, 6 figure

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

This review presents an overview of the thermal properties of mesoscopic structures. The discussion is based on the concept of electron energy distribution, and, in particular, on controlling and probing it. The temperature of an electron gas is determined by this distribution: refrigeration is equivalent to narrowing it, and thermometry is probing its convolution with a function characterizing the measuring device. Temperature exists, strictly speaking, only in quasiequilibrium in which the distribution follows the Fermi-Dirac form. Interesting nonequilibrium deviations can occur due to slow relaxation rates of the electrons, e.g., among themselves or with lattice phonons. Observation and applications of nonequilibrium phenomena are also discussed. The focus in this paper is at low temperatures, primarily below 4 K, where physical phenomena on mesoscopic scales and hybrid combinations of various types of materials, e.g., superconductors, normal metals, insulators, and doped semiconductors, open up a rich variety of device concepts. This review starts with an introduction to theoretical concepts and experimental results on thermal properties of mesoscopic structures. Then thermometry and refrigeration are examined with an emphasis on experiments. An immediate application of solid-state refrigeration and thermometry is in ultrasensitive radiation detection, which is discussed in depth. This review concludes with a summary of pertinent fabrication methods of presented devices.Comment: Close to the version published in RMP; 59 pages, 35 figure

High performance microbolometers and microcalorimeters: from 300 K to 100 mK

This thesis is a review of six publications which focus on the development of ther-mal detectors and on-chip coolers. The thermal detectors developed are antenna coupled microbolometers and transition-edge microcalorimeters. The bolometers are intended for the detection of submillimetre waves, a region in the electromag-netic spectrum located between the infrared and microwave frequencies, in which detection methods are least developed. A room temperature bolometer is pre-sented, which is suitable for applications where large levels of signal power are present, such as solar astronomy or imaging of concealed weapons under cloth-ing when combined with an illumination source, while the sensitivity of a novel superconducting bolometer, operated at 4.2 K, is more than sufficient for passive imaging of terrestrial sources. The figure of merit for this detector is shown to be about an order of magnitude better than that of existing 4.2 K bolometers. Results obtained with X-ray transition-edge sensor (TES) microcalorimeters, the most sensitive type of X-ray detector in terms of energy resolution to date, are presented. These devices are operated at temperatures below 100 mK, and can achieve energy resolutions of a few electron volts. The TES microcalorimeters wil