Terahertz real-time imaging uncooled array based on antenna- and cavity-coupled bolometers

Abstract

The development of terahertz (THz) applications is slowed down by the availability of affordable, easyto-use and highly sensitive detectors. CEA-Leti took up this challenge by tailoring the mature infrared (IR) bolometer technology for optimized THz sensing. The key feature of these detectors relies on the separation between electromagnetic absorption and the thermometer. For each pixel, specific structures of antennas and a resonant quarter-wavelength cavity couple efficiently the THz radiation on a broadband range, while a central silicon microbridge bolometer resistance is read out by a complementary metal oxide semiconductor circuit. 320 × 240 pixel arrays have been designed and manufactured: a better than 30 pW power direct detection threshold per pixel has been demonstrated in the 2-4 THz range. Such performance is expected on the whole THz range by proper tailoring of the antennas while keeping the technological stack largely unchanged. This paper gives an overview of the developed bolometer-based technology. First, it describes the technology and reports the latest performance characterizations. Then imaging demonstrations are presented, such as realtime reflectance imaging of a large surface of hidden objects and THz time-domain spectroscopy beam twodimensional profiling. Finally, perspectives of camera integration for scientific and industrial applications are discussed.

Metamaterial-Based Terahertz Imaging

“…The pixel is approximately λ/4 because of the properties of the MM system we use. This compares well with antenna coupled devices that require a pixel size of λ/2 [28,29]. The ability to operate at higher frequencies (2.5 THz as opposed to only 1 THz) also facilitates size reduction.…”

Full-Field Terahertz Imaging at Kilohertz Frame Rates Using Atomic Vapor

“…Alternatively, this result can be expressed as a minimum detectable intensity of ð0.12 AE 0.02Þ mW m −2 s −1=2 . This value represents an improvement of over 2 orders of magnitude on other roomtemperature imaging systems [16] and is the reason that such high frame rates are possible.…”

“…These schemes typically consist of arrays of small point detectors such as microbolometers [12,13], field-effect transistors (FETs) [14], or carbon nanotubes [15]. Such arrays can operate up to video frame rates of around 60 Hz; however, their sensitivities are limited, and scaling to large pixel numbers can be challenging [16]. More sensitive arrays such as those based on superconductors [17] suffer similar scaling problems and rely on cryogenic cooling to overcome thermal noise, making them cumbersome, expensive, and complex to operate.…”

Performance evaluation of active sub-Terahertz systems in Degraded Visual Environments (DVE)

“…Pixel design has been optimized for optimal sensitivity in the 1 to 3 THz range thanks to a cross polarized antenna structure backed by a quarter wavelength dielectric cavity [15]. This camera presents minimum detectable power (MDP) values of a few tens of pW, depending on the frequency.…”