We fabricated and experimentally studied a wideband metamaterial comprising a 2D array of annular antennas with Superconductor-Insulator-Normal metal-Insulator-Superconductor (SINIS) bolometers. The annular antenna array metamaterial was designed for a frequency range of 300–450 GHz and consists of periodically arranged electrically small rings, each containing two or four SINIS bolometers connected in series or parallel. These periodic structures with a unit cell size of about one-tenth of a wavelength act as a distributed absorber and receive two orthogonal polarizations. The unit’s small cell size provides a higher density of bolometers and therefore increases the bandwidth and the dynamic range of a single pixel. Theoretical estimates at a central frequency of 345 GHz yield absorption efficiencies of over 80% of the incident RF power within the 300–450 GHz frequency range. The average absorption by the metamaterial matrix in the given frequency band is at least twice as high in comparison to the half-wave circle matrix. We measured the optical response at sample temperatures as low as 100 mK using a quasi-optical setup that consisted of an immersion sapphire lens, bandpass mesh filters, and a variable temperature cryogenic blackbody radiation source. The measured series array voltage responsivity was 1.3 × 10⁹ V/W for radiation temperatures ranging from 2 K to 7.5 K. The current responsivity for the parallel array was 2.4 × 10⁴ A/W at a bath temperature of 100 mK. The spectral response was measured in a 240–370 GHz range with a Backward Wave Oscillator radiation source. The measured equivalent temperature sensitivity could be reduced to 100 μK/Hz^1/2 at a 2.7 K radiation temperature level, a value that is suitable for anisotropy measurements in cosmic microwave background radiation.

For improving the dynamic range and sensitivity at high power load we have integrated Superconductor-Insulator-Normal metal-Insulator-Superconductor (SINIS) bolometers with a Frequency Selective Surface (FSS) based distributed absorber formed by a series and parallel array consisting of 25 annular antenna elements, each containing two SINIS bolometers. By using a design with 50 bolometers we reduce incident power load on each bolometer, increase sensitivity and saturation power which is important for ground-based and balloon-borne telescopes with high background power loads. Our main detector pixel is optimized for a frequency band centered at 345 GHz. The detectors are matched to incoming telescope beam by a back-to-back horn with a back reflector. Such a configuration improves both the efficiency and the bandwidth of the receiver. Measured voltage responsivity approaches 2*109 V/W with an amplifier-limited voltage noise of 20 nV/Hz1/2, which corresponds to a NEP=10-17 W/Hz1/2. The linear voltage response for incoming power is observed for absorbed power of about 5 pW. The current responsivity for parallel array is 2*104 A/W and the shot noise limited intrinsic noise equivalent power is NEP=5*10-18 W/Hz1/2. The noise equivalent temperature difference is NETD=100 μK/Hz1/2 at 2.7 K background radiation temperature.

We have proposed a new design of the Josephson traveling-wave parametric amplifier (JTWPA) capable of providing much higher spurious-free dynamic range (SFDR). For this purpose, we substitute dc SQUIDs for bi-SQUIDs in the used artificial signal transmission line driven by external travelling-wave magnetic flux. The increase of SFDR follows from the increased linearity domain of the phase-current relation in bi-SQUID as compared to dc SQUID. Optimal parameters for bi-SQUIDs have been determined. The first version of JTWPA was modeled to be fabricated using niobium process.

This review presents the main characteristics and mechanisms of operation of superconductor–insulator–normal metal–insulator–superconductor (SINIS) microwave detectors. An analysis of the detectors’ performance against a quantum detector and a photon counter is given. Methods for cooling a superconductor using normal metal traps and the role of electron cooling in optimizing the current response to terahertz radiation are discussed. Fabrication methods using shadow evaporation as well as magnetron sputtering are described.

Bolometers based on the superconductor–insulator–normal-metal–insulator–superconductor (SINIS) structure with an absorber suspended above the substrate are developed, fabricated, and experimentally studied in the terahertz frequency range. In contrast to the previously studied bolometers with an absorber located directly on the substrate, the real bolometric mode of operation is achieved, i.e., there is more than one excited electron per quantum of electromagnetic radiation (the quantum efficiency is larger than 1). A quantum efficiency of fifteen electrons per quantum of radiation with a frequency of 350 GHz was achieved in the studied bolometers.

We have developed a bolometer with a suspended normal-metal absorber connected to superconducting leads via tunneling barriers. Such an absorber has reduced heat losses to the substrate, which greatly increases the responsivity of the bolometer to over 10⁹ V/W at 75 mK when measured by dc Joule heating of the absorber. For high-frequency experiments, the bolometers have been integrated in planar twin-slot and log-periodic antennas. At 300 GHz and 100 mK, the bolometer demonstrates the voltage and current response of 3 × 10⁸ V/W and 1.1 × 10⁴ A/W, respectively, corresponding to the quantum efficiency of ∼15 electrons per photon. An effective thermalization of electrons in the absorber favors the high quantum efficiency. We also report on how the in-plane- and transverse magnetic fields influence the device characteristics.