Review of terahertz technology development at INO

In terahertz (THz) materials science, imaging by scanning prevails when low power THz sources are used. However, the application of array detectors operating with high power THz sources is increasingly reported. We compare the imaging properties of four different array detectors that are able to record THz radiation directly. Two micro-bolometer arrays are designed for infrared imaging in the 8–14 μm wavelength range, but are based on different absorber materials (i) vanadium oxide; (ii) amorphous silicon; (iii) a micro-bolometer array optimized for recording THz radiation based on silicon nitride; and (iv) a pyroelectric array detector for THz beam profile measurements. THz wavelengths of 96.5 μm, 118.8 μm, and 393.6 μm from a powerful far infrared laser were used to assess the technical performance in terms of signal to noise ratio, detector response and detectivity. The usefulness of the detectors for beam profiling and digital holography is assessed. Finally, the potential and limitation for real-time digital holography are discussed.

Section: Introductionmentioning

confidence: 99%

Comparison of Thermal Detector Arrays for Off-Axis THz Holography and Real-Time THz Imaging

Hack

Valzania

Gäumann

et al. 2016

“…This tedious process is far from matching with the required frame-rate targeted for quality control or non-destructive testing applications in an industrial context. To face this limitation, research groups and cutting-edge technology centers have developed and are commercialising a variety of compact and uncooled terahertz matrix sensors based on several technological advances, from micro-bolometer integration to semi-conductors hetero-structures [ 13 , 14 , 15 , 16 ], in order to cover different frequency bands from 100 GHz up to 5 THz. The use of residual sensitivity of Long Wave InfraRed (LWIR) cameras in the terahertz domain has also been assessed [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

A Versatile Illumination System for Real-Time Terahertz Imaging

Perraud

Chopard

Guillet

et al. 2020

Terahertz technologies are attracting strong interest from high-end industrial fields, and particularly for non-destructive-testing purposes. Currently lacking compactness, integrability as well as adaptability for those implementations, the development and commercialisation of more efficient sources and detectors progressively ensure the transition toward applicative implementations, especially for real-time full-field imaging. In this work, a flexible illumination system, based on fast beam steering has been developed and characterized. Its primary goal is to suppress interferences induced by the coherence length of certain terahertz sources, spoiling terahertz images. The second goal is to ensure an enhanced signal-to-noise ratio on the detector side by the full use and optimized distribution of the available power. This system provides a homogeneous and adjustable illumination through a simplified setup to guarantee optimum real-time imaging capabilities, tailored to the sample under inspection. Working toward industrial implementations, different illumination process are conveniently assessed as a result of the versatility of this method.

“…Values of minimum detectable powers per pixel were comparable with those of other compact THz detectors, such as uncooled field effect transistor (FET) THz sensors and cooled bolometer arrays demonstrating large potential in the frequency range of 0.3–4.3 THz. On the other hand, the French Institut National d’Optique (INO) has developed a THz imaging system capable of detecting concealed weapons or hidden objects behind drywall, and for non-destructive testing military applications [ 11 ]. The imaging system was based on the THz cameras built at INO, for example, the THz-optimized IRXCAM-THz-160 and IRXCAM-THz-384 cameras that support the 160 × 120 and 384 × 288 uncooled microbolometer pixel array with a pixel pitch of 52 μm and 35 μm, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…The imaging system was based on the THz cameras built at INO, for example, the THz-optimized IRXCAM-THz-160 and IRXCAM-THz-384 cameras that support the 160 × 120 and 384 × 288 uncooled microbolometer pixel array with a pixel pitch of 52 μm and 35 μm, respectively. The sensitivity of INO’s THz detectors was determined by NEP values reaching up to 25 pW/√Hz and 76 pW/√Hz at frequencies of 4.25 THz and 2.54 THz, respectively [ 11 ]. The NEP dependence on the wavelength was explained by differences in pixel size, detector bandwidth, and pixel responsivity.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Terahertz Imaging at Room Temperature Employing Microbolometer Terahertz Sensors and Its Application to the Study of Carcinoma Tissues

Kašalynas

Venckevičius

Minkevičius

et al. 2016

A terahertz (THz) imaging system based on narrow band microbolometer sensors (NBMS) and a novel diffractive lens was developed for spectroscopic microscopy applications. The frequency response characteristics of the THz antenna-coupled NBMS were determined employing Fourier transform spectroscopy. The NBMS was found to be a very sensitive frequency selective sensor which was used to develop a compact all-electronic system for multispectral THz measurements. This system was successfully applied for principal components analysis of optically opaque packed samples. A thin diffractive lens with a numerical aperture of 0.62 was proposed for the reduction of system dimensions. The THz imaging system enhanced with novel optics was used to image for the first time non-neoplastic and neoplastic human colon tissues with close to wavelength-limited spatial resolution at 584 GHz frequency. The results demonstrated the new potential of compact RT THz imaging systems in the fields of spectroscopic analysis of materials and medical diagnostics.