Faustin Carter

Development of the nano-HEB array for low-background far-IR applications

We present an overview of the recent progress made in the development of a far-IR array of ultrasensitive hot-electron nanobolometers (nano-HEB) made from thin titanium (Ti) films. We studied electrical noise, signal and noise bandwidth, single-photon detection, optical noise equivalent power (NEP), and a microwave SQUID (MSQUID) based frequency domain multiplexing (FDM) scheme. The obtained results demonstrate the very low electrical NEP down to 1.5×10-20 W/Hz1/2 at 50 mK determined by the dominating phonon noise. The NEP increases with temperature as ~ T3 reaching ~ 10-17 W/Hz1/2 at the device critical temperature TC = 330-360 mK. Optical NEP = 8.6×10-18 W/Hz1/2 at 357 mK and 1.4×10-18 W/Hz1/2 at 100 mK respectively, agree with thermal and electrical data. The optical coupling efficiency provided by a planar antenna was greater than 50%. Single 8-μm photons have been detected for the first time using a nano-HEB operating at 50-200 mK thus demonstrating a potential of these detectors for future photon-counting applications in mid-IR and far-IR. In order to accommodate the relatively high detector speed (~ μs at 300 mK, ~ 100 μs at 100 mK), an MSQUID based FDM multiplexed readout with GHz carrier frequencies has been built. Both the readout noise ~ 2 pA/Hz1/2 and the bandwidth > 150 kHz are suitable for nano-HEB detectors.

A plasmonic antenna-coupled superconducting near-IR photon detector

The extremely small size of plasmonic antennas has made it difficult to integrate them with nanoscale detectors that require electrical leads, as the leads tend to degrade the resonant properties of the antenna. We present a design for integrating a plasmonic antenna with a nanoscale superconducting transition-edge sensor (TES) with electrical leads. Numerical simulations demonstrate high-efficiency coupling of 1550 nm incident photons into the sub-wavelength TES. Although we have chosen to design around a TES, this approach is broadly applicable to any dissipative nanoscale device that requires an electrical connection.

Proposal for a GHz count rate near-IR single-photon detector based on a nanoscale superconducting transition edge sensor

We describe a superconducting transition edge sensor based on a nanoscale niobium detector element. This device is predicted to be capable of energy-resolved near-IR single-photon detection with a GHz count rate. The increased speed and sensitivity of this device compared to traditional transition edge sensors result from the very small electronic heat capacity of the nanoscale detector element. In the present work, we calculate the predicted thermal response time and energy resolution. We also discuss approaches for achieving efficient optical coupling to the sub-wavelength detector element using a resonant near-IR antenna.

Toward the In Situ Detection of Individual Excimers Using a Ti TES in Superfluid Helium

We characterize a single titanium (Ti) transition edge sensor (TES) designed for in situ detection of individual He2 excimers. We find a critical temperature of 420 mK, an electrothermal time constant of ~3 μs, and a total energy resolution of 1.5 eV. We observe the detector response to short laser pulses and present a successful analysis strategy for extracting direct-TES-hit pulses from a much larger background (due to substrate hits). We also present the response of a similar Ti TES with a built-in aperture designed to eliminate substrate background; this device has an energy resolution of better than 1.5 eV and a much reduced substrate signal. We discuss near-term plans for coupling multiple such TESs together with a shared aluminum (Al) absorber, increasing the He2 collection area to millimeter scales.

Calorimetric Observation of Single \hbox {He}_2^* Excimers in a 100-mK He Bath

We report the first calorimetric detection of individual

Enhanced Brillouin scattering in silica via saturable phonon losses

\hbox {He}_2^*

_{2}

He2∗ excimers within a bath of superfluid