Andrew D. Beyer

A Near-Infrared 64-pixel Superconducting Nanowire Single Photon Detector Array with Integrated Multiplexed Readout

We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.

Characterizing SixNy absorbers and support beams for far-infrared/submillimeter transition-edge sensors

We report on the characterization of SixNy (Si-N) optical absorbers and support beams for transition-edge sensors (TESs). The absorbers and support beams measured are suitable to meet ultra-sensitive noise equivalent power (NEP≤10-19W/√Hz) and effective response time (τ) requirements (τ≤100ms) for space-borne far-infrared( IR)/submillimeter(sub-mm) spectrometers, such as the Background Limited far-Infrared/Sub-mm Spectrograph (BLISS) and the SpicA FAR-infrared Instrument (SAFARI) for the SPace Infrared telescope for Cosmology and Astrophysics (SPICA). The thermal response time (τ0) of an absorber suspended by support beams from a lowtemperature substrate depends on the heat capacity (C) of the absorber and the thermal conductance (G) of the support beams (τ0=C/G). In membrane-isolated TESs for BLISS, the effective response time τ is expected to be a factor of 20 smaller than τ0 because of voltage-biased electrothermal feedback operation and assumption of a reasonable open-loop gain, LI≈20. We present design specifications for the arrays of membrane-isolated ultra-sensitive TESs for BLISS. Additionally, we measured G and τ0 for two Si-N noise thermometry device (NTD) architectures made using different fabrication processes: (1) a solid membrane Si-N absorber suspended by thin and long Si-N support beams and (2) a wire-mesh Si-N absorber suspended by long, and even thinner, Si-N support beams. The measurements of G and τ0 were designed to test suitability of the Si-N thermal performance to meet the demands of the two SPICA instruments. The solid membrane NTD architecture is similar to the TES architecture for SAFARI and the mesh membrane NTD is similar to that of BLISS TESs. We report measured values of G and C for several BLISS and SAFARI NTD devices. We observe that the heat capacity of the solid membrane devices can be reduced to the order of 1fJ/K at 65mK for devices that are wet etched by KOH. However, C for these devices is found to be on the order of 100fJ/K for a dry XeF2 process. The heat capacity is similarly large for the mesh devices produced with a dry XeF2 etch.Next generation cosmic microwave background (CMB) polarization anisotropy measurements will feature focal plane arrays with more than 600 millimeter-wave detectors. We make use of high-resolution photolithography and wafer-scale etch tools to build planar arrays of corrugated platelet feeds in silicon with highly symmetric beams, low cross-polarization and low side lobes. A compact Au-plated corrugated Si feed designed for 150 GHz operation exhibited performance equivalent to that of electroformed feeds: ∼ −0.2 dB insertion loss, < −20 dB return loss from 120 GHz to 170 GHz, < −25 dB side lobes and < −23 dB cross-polarization. We are currently fabricating a 50mm diameter array with 84 horns consisting of 33 Si platelets as a prototype for the SPTpol and ACTpol telescopes. Our fabrication facilities permit arrays up to 150mm in diameter.

Progress Towards a Near IR Single-Photon Superconducting Nanowire Camera for Free-Space Imaging of Light

We describe our progress towards building a free-space coupled array of nanowire detectors with a multiplexed readout. The cryogenic, optical, and electronic packaging to readout the array will be discussed.

The background-limited infrared-submillimeter spectrograph (BLISS) for SPICA: a design study

We are developing the Background-Limited Infrared-Submillimeter Spectrograph (BLISS) for SPICA to provide a breakthrough capability for far-IR survey spectroscopy. SPICAs large cold aperture allows mid-IR to submm observations which are limited only by the natural backgrounds, and BLISS is designed to operate near this fundamental limit. BLISS-SPICA is 6 orders of magnitude faster than the spectrometers on Herschel and SOFIA in obtaining full-band spectra. It enables spectroscopy of dust-obscured galaxies at all epochs back to the rst billion years after the Big Bang (redshift 6), and study of all stages of planet formation in circumstellar disks. BLISS covers 35 - 433 microns range in ve or six wavelength bands, and couples two 2 sky positions simultaneously. The instrument is cooled to 50 mK for optimal sensitivity with an on-board refrigerators. The detector package is 4224 silicon-nitride micro-mesh leg-isolated bolometers with superconducting transition-edge-sensed (TES) thermistors, read out with a cryogenic time-domain multiplexer. All technical elements of BLISS have heritage in mature scientic instruments, and many have own. We report on our design study in which we are optimizing performance while accommodating SPICAs constraints, including the stringent cryogenic mass budget. In particular, we present our progress in the optical design and waveguide spectrometer prototyping. A companion paper in Conference 7741 (Beyer et al.) discusses in greater detail the progress in the BLISS TES bolometer development.

Development of fast, background-limited transition-edge sensors for the Background-Limited Infrared/Sub-mm Spectrograph (BLISS) for SPICA

We report experimental progress toward demonstrating background-limited arrays of membrane-isolated transition-edge sensors (TESs) for the Background Limited Infrared/Sub-mm Spectrograph (BLISS). BLISS is a space-borne instrument with grating spectrometers for wavelengths λ= 35-435 μm and with R= λ/Δλ~500. The goals for BLISS TESs are: noise equivalent power (NEP) = 5×10^-20 W/Hz^1/2 and response time τ<30ms. We expect background-limited performance from bilayers TESs with T_C=65mK and G=15fW/K. However, such TESs cannot be operated at 50mK unless stray power on the devices, or dark power P_D, is less than 200aW. We describe criteria for measuring P_D that requires accurate knowledge of T_C. Ultimately, we fabricated superconducting thermistors from Ir (T_C≥135mK) and Mo/Cu proximitized bilayers, where T_C is the thermistor transition temperature. We measured the Ir TES arrays in our 45mK base temperature adiabatic demagnetization refrigerator test system, which can measure up to eight 1x32 arrays simultaneously using a time-division multiplexer, as well as our single-pixel test system which can measure down to 15mK. In our previous Ir array measurements our best reported performance was NEP=2.5×10^-19 W/Hz^1/2 and τ~5ms for straight-beam TESs. In fact, we expected NEP 1.5×10^-19W/Hz^1/2for meander beam TESs, but did not achieve this previously due to 1/f noise. Here, we detail improvements toward measuring the expected NEP and demonstrate NEP=(1.3±0.2)×10^-19W/Hz^1/2 in our single-pixel test system and NEP=(1.6±0.3)×10^-19W/Hz^1/2 in our array test system.

High-dimensional time-energy entanglement-based quantum key distribution using dispersive optics

We implement a high-dimensional quantum key distribution protocol secure against collective attacks. We transform between conjugate measurement bases using group velocity dispersion. We obtain > 3 secure bits per photon coincidence.

Nanowire superconducting single photon detectors progress and promise

Since the first reported detection of a single photon using a superconducting nanowire in 2001, rapid progress has been made in the development and application of superconducting nanowire single photon detectors (SNSPD or SSPD). I will briefly describe use of these detectors in new applications, progress in detector developments, and describe areas of research and their potential impact.

Design of antenna-coupled lumped-element titanium nitride KIDs for long-wavelength multi-band continuum imaging

Many applications in cosmology and astrophysics at millimeter wavelengths — CMB polarization, studies of galaxy clusters using the Sunyaev-Zeldovich effect, studies of star formation at high redshift and in our local universe and our galaxy— require large-format arrays of millimeter-wave detectors. Feedhorn, lens-coupled twinslot antenna, and phased-array antenna architectures for receiving mm-wave light present numerous advantages for control of systematics and for simultaneous coverage of both polarizations and/or multiple spectral bands. Simultaneously, kinetic inductance detectors using high-resistivity materials like titanium nitride are an attractive sensor option for large-format arrays because they are highly multiplexable and because their high responsivity can render two-level-system noise subdominant to photon and recombination noise. However, coupling the two is a challenge because of the impedance mismatch between the microstrip exiting these architectures and the high resistivity of titanium nitride. Mitigating direct absorption in the KID is also a challenge. We present a detailed titanium nitride KID design that addresses these challenges. The KID inductor is capacitively coupled to the microstrip in such a way as to form a lossy termination without creating an impedance mismatch. A parallelplate capacitor design mitigates direct absorption, uses hydrogenated amorphous silicon, and yields acceptable two-level-system noise. We show that an optimized design can yield expected sensitivities very close to the fundamental limit from photon and recombination noises for two relevant examples: single spectral band designs appropriate for 90 and 150 GHz for CMB polarization and a multi-spectral-band design that covers 90 GHz to 405 GHz in six bands for SZ effect studies.

Superconducting nanowire single photon detectors for deep space optical communication (Conference Presentation)

The Deep Space Optical Communication (DSOC) project at the Jet Propulsion Laboratory aims to perform a bidirectional laser communication technology demonstration from deep space, at ranges from 0.1 - 3 AU. To support high data rates over such distances while keeping the mass and power on the spacecraft comparable to radio-frequency communication systems, extremely high-performance single photon detectors are required at the ground receiver. To this end, JPL has been developing 64-pixel tungsten silicide superconducting nanowire single photon detector (WSi SNSPD) arrays suitable for use in the DSOC ground terminal. To efficiently couple to a 5-meter telescope aperture in the presence of atmospheric seeing, the arrays are free-space coupled and have a combined 320-micron diameter active area. The development is targeting 70% system detection efficiency at an operating wavelength of 1550 nm, 150 ps time resolution, a maximum count rate approaching 109 counts per second, a numerical aperture capable of supporting an f/1.2 beam, a background-limited dark count rate, and an operating temperature of 1 Kelvin. In this paper, we will present our progress toward these goals, both in terms of focal plane array development and cryogenic readout technology.

Recent advances in superconducting nanowire single photon detectors for single-photon imaging

We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.