A passive terahertz video camera based on lumped element kinetic inductance detectors

Abstract

We have developed a passive 350 GHz (850 μm) video-camera to demonstrate lumped element kinetic inductance detectors (LEKIDs)--designed originally for far-infrared astronomy--as an option for general purpose terrestrial terahertz imaging applications. The camera currently operates at a quasi-video frame rate of 2 Hz with a noise equivalent temperature difference per frame of ∼0.1 K, which is close to the background limit. The 152 element superconducting LEKID array is fabricated from a simple 40 nm aluminum film on a silicon dielectric substrate and is read out through a single microwave feedline with a cryogenic low noise amplifier and room temperature frequency domain multiplexing electronics.

Optomechanical System Design for Dual-Mode Stand-Off Submillimeter Wavelength Imagers

“…Moreover, the signal penetration through the clothing is still sufficient for detection at these frequencies. Several sub-millimeter wave imagers are currently available in the literature [3]- [11], using passive or active schemes. Table I summarizes the current state-of-the-art of these systems.…”

“…The current submillimeter wavelength imagers suffer from low speeds and/or limited Field of Views (FOV) due to the lack of integrated array technology at these frequencies. Passive imagers have been demonstrated using up to approximately 100 cooled detectors [8]- [11]. Instead, the development of active submillimeter wave imagers has been focused on single pixel architectures [4]- [7].…”

Cryogenic LED pixel-to-frequency mapper for kinetic inductance detector arrays

“…MKIDs have received great attention in astronomy [6][7][8] and other sensitive detection fields [9,10] because they are simple to fabricate and easy to multiplex into large arrays. A MKID array with thousands of pixels can be fabricated with one or a few standard photo-lithography steps and read out with a pair of coaxial cables into the cryostat.…”

Design and Characterisation of Titanium Nitride Subarrays of Kinetic Inductance Detectors for Passive Terahertz Imaging

“…MKIDs have the advantage of relatively simple fabrication and scalability which makes them a technology of choice for building an imager with large numbers of pixels [6]. Recently, arrays of MKIDs, predominantly used in astronomical instruments, were successfully used in a THz camera built by Cardiff University [7]. With lumped-element MKIDs (LEKIDs) based on Al films, a demonstration camera achieved quasi-video frame rate of 2 Hz and noise equivalent differential temperature, K at 350 GHz.…”

“…For practical applications in security, image rate of 25 frames per second with NEDT 0.1 K per frame is desirable. For a 350 GHz imager with linear array of detectors, similar to the one reported in [7], each pixel needs to have a time constant of  100  and photon-noise-limited NEP with the optical load of few hundreds pW, where exact values depend on the system’s optical bandwidth and background temperature. TiN resonator devices were characterised previously by a number of groups.…”